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Conducting a literature review: why do a literature review, why do a literature review.

• How To Find "The Literature"
• Found it -- Now What?

Besides the obvious reason for students -- because it is assigned! -- a literature review helps you explore the research that has come before you, to see how your research question has (or has not) already been addressed.

You identify:

• core research in the field
• experts in the subject area
• methodology you may want to use (or avoid)
• gaps in knowledge -- or where your research would fit in

It Also Helps You:

• Publish and share your findings
• Justify requests for grants and other funding
• Identify best practices to inform practice
• Set wider context for a program evaluation
• Compile information to support community organizing

Great brief overview, from NCSU

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Why is it important to do a literature review in research?

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 “A substantive, thorough, sophisticated literature review is a precondition for doing substantive, thorough, sophisticated research”. Boote and Baile 2005

Authors of manuscripts treat writing a literature review as a routine work or a mere formality. But a seasoned one knows the purpose and importance of a well-written literature review.  Since it is one of the basic needs for researches at any level, they have to be done vigilantly. Only then the reader will know that the basics of research have not been neglected.

The aim of any literature review is to summarize and synthesize the arguments and ideas of existing knowledge in a particular field without adding any new contributions.   Being built on existing knowledge they help the researcher to even turn the wheels of the topic of research.  It is possible only with profound knowledge of what is wrong in the existing findings in detail to overpower them.  For other researches, the literature review gives the direction to be headed for its success. 

The common perception of literature review and reality:

As per the common belief, literature reviews are only a summary of the sources related to the research. And many authors of scientific manuscripts believe that they are only surveys of what are the researches are done on the chosen topic.  But on the contrary, it uses published information from pertinent and relevant sources like

• Scholarly books
• Scientific papers
• Latest studies in the field
• Established school of thoughts
• Relevant articles from renowned scientific journals

and many more for a field of study or theory or a particular problem to do the following:

• Summarize into a brief account of all information
• Synthesize the information by restructuring and reorganizing
• Critical evaluation of a concept or a school of thought or ideas
• Familiarize the authors to the extent of knowledge in the particular field
• Encapsulate
• Compare & contrast

By doing the above on the relevant information, it provides the reader of the scientific manuscript with the following for a better understanding of it:

• It establishes the authors’  in-depth understanding and knowledge of their field subject
• It gives the background of the research
• Portrays the scientific manuscript plan of examining the research result
• Illuminates on how the knowledge has changed within the field
• Highlights what has already been done in a particular field
• Information of the generally accepted facts, emerging and current state of the topic of research
• Identifies the research gap that is still unexplored or under-researched fields
• Demonstrates how the research fits within a larger field of study
• Provides an overview of the sources explored during the research of a particular topic

Importance of literature review in research:

The importance of literature review in scientific manuscripts can be condensed into an analytical feature to enable the multifold reach of its significance.  It adds value to the legitimacy of the research in many ways:

• Provides the interpretation of existing literature in light of updated developments in the field to help in establishing the consistency in knowledge and relevancy of existing materials
• It helps in calculating the impact of the latest information in the field by mapping their progress of knowledge.
• It brings out the dialects of contradictions between various thoughts within the field to establish facts
• The research gaps scrutinized initially are further explored to establish the latest facts of theories to add value to the field
• Indicates the current research place in the schema of a particular field
• Provides information for relevancy and coherency to check the research
• Apart from elucidating the continuance of knowledge, it also points out areas that require further investigation and thus aid as a starting point of any future research
• Justifies the research and sets up the research question
• Sets up a theoretical framework comprising the concepts and theories of the research upon which its success can be judged
• Helps to adopt a more appropriate methodology for the research by examining the strengths and weaknesses of existing research in the same field
• Increases the significance of the results by comparing it with the existing literature
• Provides a point of reference by writing the findings in the scientific manuscript
• Helps to get the due credit from the audience for having done the fact-finding and fact-checking mission in the scientific manuscripts
• The more the reference of relevant sources of it could increase more of its trustworthiness with the readers
• Helps to prevent plagiarism by tailoring and uniquely tweaking the scientific manuscript not to repeat other’s original idea
• By preventing plagiarism , it saves the scientific manuscript from rejection and thus also saves a lot of time and money
• Helps to evaluate, condense and synthesize gist in the author’s own words to sharpen the research focus
• Helps to compare and contrast to  show the originality and uniqueness of the research than that of the existing other researches
• Rationalizes the need for conducting the particular research in a specified field
• Helps to collect data accurately for allowing any new methodology of research than the existing ones
• Enables the readers of the manuscript to answer the following questions of its readers for its better chances for publication
• What do the researchers know?
• What do they not know?
• Is the scientific manuscript reliable and trustworthy?
• What are the knowledge gaps of the researcher?

22. It helps the readers to identify the following for further reading of the scientific manuscript:

• What has been already established, discredited and accepted in the particular field of research
• Areas of controversy and conflicts among different schools of thought
• Unsolved problems and issues in the connected field of research
• The emerging trends and approaches
• How the research extends, builds upon and leaves behind from the previous research

A profound literature review with many relevant sources of reference will enhance the chances of the scientific manuscript publication in renowned and reputed scientific journals .

References:

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• Steps in Conducting a Literature Review

What is a literature review?

A literature review is an integrated analysis -- not just a summary-- of scholarly writings and other relevant evidence related directly to your research question.  That is, it represents a synthesis of the evidence that provides background information on your topic and shows a association between the evidence and your research question.

A literature review may be a stand alone work or the introduction to a larger research paper, depending on the assignment.  Rely heavily on the guidelines your instructor has given you.

Why is it important?

A literature review is important because it:

• Explains the background of research on a topic.
• Demonstrates why a topic is significant to a subject area.
• Discovers relationships between research studies/ideas.
• Identifies major themes, concepts, and researchers on a topic.
• Identifies critical gaps and points of disagreement.
• Discusses further research questions that logically come out of the previous studies.

APA7 Style resources

APA Style Blog - for those harder to find answers

1. Choose a topic. Define your research question.

Your literature review should be guided by your central research question.  The literature represents background and research developments related to a specific research question, interpreted and analyzed by you in a synthesized way.

• Make sure your research question is not too broad or too narrow.  Is it manageable?
• Begin writing down terms that are related to your question. These will be useful for searches later.
• If you have the opportunity, discuss your topic with your professor and your class mates.

2. Decide on the scope of your review

How many studies do you need to look at? How comprehensive should it be? How many years should it cover? 

• This may depend on your assignment.  How many sources does the assignment require?

3. Select the databases you will use to conduct your searches.

Make a list of the databases you will search. 

Where to find databases:

• use the tabs on this guide
• Find other databases in the Nursing Information Resources web page
• More on the Medical Library web page
• ... and more on the Yale University Library web page

4. Conduct your searches to find the evidence. Keep track of your searches.

• Use the key words in your question, as well as synonyms for those words, as terms in your search. Use the database tutorials for help.
• Save the searches in the databases. This saves time when you want to redo, or modify, the searches. It is also helpful to use as a guide is the searches are not finding any useful results.
• Review the abstracts of research studies carefully. This will save you time.
• Use the bibliographies and references of research studies you find to locate others.
• Check with your professor, or a subject expert in the field, if you are missing any key works in the field.
• Ask your librarian for help at any time.
• Use a citation manager, such as EndNote as the repository for your citations. See the EndNote tutorials for help.

Review the literature

Some questions to help you analyze the research:

• What was the research question of the study you are reviewing? What were the authors trying to discover?
• Was the research funded by a source that could influence the findings?
• What were the research methodologies? Analyze its literature review, the samples and variables used, the results, and the conclusions.
• Does the research seem to be complete? Could it have been conducted more soundly? What further questions does it raise?
• If there are conflicting studies, why do you think that is?
• How are the authors viewed in the field? Has this study been cited? If so, how has it been analyzed?

Tips: 

• Review the abstracts carefully.  
• Keep careful notes so that you may track your thought processes during the research process.
• Create a matrix of the studies for easy analysis, and synthesis, across all of the studies.
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• Literature Review: The What, Why and How-to Guide
• Introduction

Literature Review: The What, Why and How-to Guide — Introduction

• Getting Started
• How to Pick a Topic
• Strategies to Find Sources
• Evaluating Sources & Lit. Reviews
• Tips for Writing Literature Reviews
• Writing Literature Review: Useful Sites
• Citation Resources
• Other Academic Writings

What are Literature Reviews?

So, what is a literature review? "A literature review is an account of what has been published on a topic by accredited scholars and researchers. In writing the literature review, your purpose is to convey to your reader what knowledge and ideas have been established on a topic, and what their strengths and weaknesses are. As a piece of writing, the literature review must be defined by a guiding concept (e.g., your research objective, the problem or issue you are discussing, or your argumentative thesis). It is not just a descriptive list of the material available, or a set of summaries." Taylor, D.  The literature review: A few tips on conducting it . University of Toronto Health Sciences Writing Centre.

Goals of Literature Reviews

What are the goals of creating a Literature Review?  A literature could be written to accomplish different aims:

• To develop a theory or evaluate an existing theory
• To summarize the historical or existing state of a research topic
• Identify a problem in a field of research 

Baumeister, R. F., & Leary, M. R. (1997). Writing narrative literature reviews .  Review of General Psychology , 1 (3), 311-320.

What kinds of sources require a Literature Review?

• A research paper assigned in a course
• A thesis or dissertation
• A grant proposal
• An article intended for publication in a journal

All these instances require you to collect what has been written about your research topic so that you can demonstrate how your own research sheds new light on the topic.

Types of Literature Reviews

What kinds of literature reviews are written?

Narrative review: The purpose of this type of review is to describe the current state of the research on a specific topic/research and to offer a critical analysis of the literature reviewed. Studies are grouped by research/theoretical categories, and themes and trends, strengths and weakness, and gaps are identified. The review ends with a conclusion section which summarizes the findings regarding the state of the research of the specific study, the gaps identify and if applicable, explains how the author's research will address gaps identify in the review and expand the knowledge on the topic reviewed.

• Example : Predictors and Outcomes of U.S. Quality Maternity Leave: A Review and Conceptual Framework:  10.1177/08948453211037398  

Systematic review : "The authors of a systematic review use a specific procedure to search the research literature, select the studies to include in their review, and critically evaluate the studies they find." (p. 139). Nelson, L. K. (2013). Research in Communication Sciences and Disorders . Plural Publishing.

• Example : The effect of leave policies on increasing fertility: a systematic review:  10.1057/s41599-022-01270-w

Meta-analysis : "Meta-analysis is a method of reviewing research findings in a quantitative fashion by transforming the data from individual studies into what is called an effect size and then pooling and analyzing this information. The basic goal in meta-analysis is to explain why different outcomes have occurred in different studies." (p. 197). Roberts, M. C., & Ilardi, S. S. (2003). Handbook of Research Methods in Clinical Psychology . Blackwell Publishing.

• Example : Employment Instability and Fertility in Europe: A Meta-Analysis:  10.1215/00703370-9164737

Meta-synthesis : "Qualitative meta-synthesis is a type of qualitative study that uses as data the findings from other qualitative studies linked by the same or related topic." (p.312). Zimmer, L. (2006). Qualitative meta-synthesis: A question of dialoguing with texts .  Journal of Advanced Nursing , 53 (3), 311-318.

• Example : Women’s perspectives on career successes and barriers: A qualitative meta-synthesis:  10.1177/05390184221113735

Literature Reviews in the Health Sciences

• UConn Health subject guide on systematic reviews Explanation of the different review types used in health sciences literature as well as tools to help you find the right review type
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Literature Reviews

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What is a Literature Review?

A literature or narrative review is a comprehensive review and analysis of the published literature on a specific topic or research question. The literature that is reviewed contains: books, articles, academic articles, conference proceedings, association papers, and dissertations. It contains the most pertinent studies and points to important past and current research and practices. It provides background and context, and shows how your research will contribute to the field. 

A literature review should: 

• Provide a comprehensive and updated review of the literature;
• Explain why this review has taken place;
• Articulate a position or hypothesis;
• Acknowledge and account for conflicting and corroborating points of view

From  S age Research Methods

Purpose of a Literature Review

A literature review can be written as an introduction to a study to:

• Demonstrate how a study fills a gap in research
• Compare a study with other research that's been done

Or it can be a separate work (a research article on its own) which:

• Organizes or describes a topic
• Describes variables within a particular issue/problem

Limitations of a Literature Review

Some of the limitations of a literature review are:

• It's a snapshot in time. Unlike other reviews, this one has beginning, a middle and an end. There may be future developments that could make your work less relevant.
• It may be too focused. Some niche studies may miss the bigger picture.
• It can be difficult to be comprehensive. There is no way to make sure all the literature on a topic was considered.
• It is easy to be biased if you stick to top tier journals. There may be other places where people are publishing exemplary research. Look to open access publications and conferences to reflect a more inclusive collection. Also, make sure to include opposing views (and not just supporting evidence).

Source: Grant, Maria J., and Andrew Booth. “A Typology of Reviews: An Analysis of 14 Review Types and Associated Methodologies.” Health Information & Libraries Journal, vol. 26, no. 2, June 2009, pp. 91–108. Wiley Online Library, doi:10.1111/j.1471-1842.2009.00848.x.

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For help in other subject areas, please see the guide to library specialists by subject .

Periodically, UT Libraries runs a workshop covering the basics and library support for literature reviews. While we try to offer these once per academic year, we find providing the recording to be helpful to community members who have missed the session. Following is the most recent recording of the workshop, Conducting a Literature Review. To view the recording, a UT login is required.

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Conducting a Literature Review

Benefits of conducting a literature review.

• Steps in Conducting a Literature Review
• Summary of the Process
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• Literature Review Tutorial by American University Library
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• Write a Literature Review by UC Santa Cruz University Library

While there might be many reasons for conducting a literature review, following are four key outcomes of doing the review.

Assessment of the current state of research on a topic . This is probably the most obvious value of the literature review. Once a researcher has determined an area to work with for a research project, a search of relevant information sources will help determine what is already known about the topic and how extensively the topic has already been researched.

Identification of the experts on a particular topic . One of the additional benefits derived from doing the literature review is that it will quickly reveal which researchers have written the most on a particular topic and are, therefore, probably the experts on the topic. Someone who has written twenty articles on a topic or on related topics is more than likely more knowledgeable than someone who has written a single article. This same writer will likely turn up as a reference in most of the other articles written on the same topic. From the number of articles written by the author and the number of times the writer has been cited by other authors, a researcher will be able to assume that the particular author is an expert in the area and, thus, a key resource for consultation in the current research to be undertaken.

Identification of key questions about a topic that need further research . In many cases a researcher may discover new angles that need further exploration by reviewing what has already been written on a topic. For example, research may suggest that listening to music while studying might lead to better retention of ideas, but the research might not have assessed whether a particular style of music is more beneficial than another. A researcher who is interested in pursuing this topic would then do well to follow up existing studies with a new study, based on previous research, that tries to identify which styles of music are most beneficial to retention.

Determination of methodologies used in past studies of the same or similar topics.  It is often useful to review the types of studies that previous researchers have launched as a means of determining what approaches might be of most benefit in further developing a topic. By the same token, a review of previously conducted studies might lend itself to researchers determining a new angle for approaching research.

Upon completion of the literature review, a researcher should have a solid foundation of knowledge in the area and a good feel for the direction any new research should take. Should any additional questions arise during the course of the research, the researcher will know which experts to consult in order to quickly clear up those questions.

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Frequently asked questions

What is the purpose of a literature review.

There are several reasons to conduct a literature review at the beginning of a research project:

• To familiarize yourself with the current state of knowledge on your topic
• To ensure that you’re not just repeating what others have already done
• To identify gaps in knowledge and unresolved problems that your research can address
• To develop your theoretical framework and methodology
• To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

Frequently asked questions: Academic writing

A rhetorical tautology is the repetition of an idea of concept using different words.

Rhetorical tautologies occur when additional words are used to convey a meaning that has already been expressed or implied. For example, the phrase “armed gunman” is a tautology because a “gunman” is by definition “armed.”

A logical tautology is a statement that is always true because it includes all logical possibilities.

Logical tautologies often take the form of “either/or” statements (e.g., “It will rain, or it will not rain”) or employ circular reasoning (e.g., “she is untrustworthy because she can’t be trusted”).

You may have seen both “appendices” or “appendixes” as pluralizations of “ appendix .” Either spelling can be used, but “appendices” is more common (including in APA Style ). Consistency is key here: make sure you use the same spelling throughout your paper.

The purpose of a lab report is to demonstrate your understanding of the scientific method with a hands-on lab experiment. Course instructors will often provide you with an experimental design and procedure. Your task is to write up how you actually performed the experiment and evaluate the outcome.

In contrast, a research paper requires you to independently develop an original argument. It involves more in-depth research and interpretation of sources and data.

A lab report is usually shorter than a research paper.

The sections of a lab report can vary between scientific fields and course requirements, but it usually contains the following:

• Title: expresses the topic of your study
• Abstract: summarizes your research aims, methods, results, and conclusions
• Introduction: establishes the context needed to understand the topic
• Method: describes the materials and procedures used in the experiment
• Results: reports all descriptive and inferential statistical analyses
• Discussion: interprets and evaluates results and identifies limitations
• Conclusion: sums up the main findings of your experiment
• References: list of all sources cited using a specific style (e.g. APA)
• Appendices: contains lengthy materials, procedures, tables or figures

A lab report conveys the aim, methods, results, and conclusions of a scientific experiment . Lab reports are commonly assigned in science, technology, engineering, and mathematics (STEM) fields.

The abstract is the very last thing you write. You should only write it after your research is complete, so that you can accurately summarize the entirety of your thesis , dissertation or research paper .

If you’ve gone over the word limit set for your assignment, shorten your sentences and cut repetition and redundancy during the editing process. If you use a lot of long quotes , consider shortening them to just the essentials.

If you need to remove a lot of words, you may have to cut certain passages. Remember that everything in the text should be there to support your argument; look for any information that’s not essential to your point and remove it.

To make this process easier and faster, you can use a paraphrasing tool . With this tool, you can rewrite your text to make it simpler and shorter. If that’s not enough, you can copy-paste your paraphrased text into the summarizer . This tool will distill your text to its core message.

Revising, proofreading, and editing are different stages of the writing process .

• Revising is making structural and logical changes to your text—reformulating arguments and reordering information.
• Editing refers to making more local changes to things like sentence structure and phrasing to make sure your meaning is conveyed clearly and concisely.
• Proofreading involves looking at the text closely, line by line, to spot any typos and issues with consistency and correct them.

The literature review usually comes near the beginning of your thesis or dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a thesis, dissertation , or research paper , in order to situate your work in relation to existing knowledge.

Avoid citing sources in your abstract . There are two reasons for this:

• The abstract should focus on your original research, not on the work of others.
• The abstract should be self-contained and fully understandable without reference to other sources.

There are some circumstances where you might need to mention other sources in an abstract: for example, if your research responds directly to another study or focuses on the work of a single theorist. In general, though, don’t include citations unless absolutely necessary.

An abstract is a concise summary of an academic text (such as a journal article or dissertation ). It serves two main purposes:

• To help potential readers determine the relevance of your paper for their own research.
• To communicate your key findings to those who don’t have time to read the whole paper.

Abstracts are often indexed along with keywords on academic databases, so they make your work more easily findable. Since the abstract is the first thing any reader sees, it’s important that it clearly and accurately summarizes the contents of your paper.

In a scientific paper, the methodology always comes after the introduction and before the results , discussion and conclusion . The same basic structure also applies to a thesis, dissertation , or research proposal .

Depending on the length and type of document, you might also include a literature review or theoretical framework before the methodology.

Whether you’re publishing a blog, submitting a research paper , or even just writing an important email, there are a few techniques you can use to make sure it’s error-free:

• Take a break : Set your work aside for at least a few hours so that you can look at it with fresh eyes.
• Proofread a printout : Staring at a screen for too long can cause fatigue – sit down with a pen and paper to check the final version.
• Use digital shortcuts : Take note of any recurring mistakes (for example, misspelling a particular word, switching between US and UK English , or inconsistently capitalizing a term), and use Find and Replace to fix it throughout the document.

If you want to be confident that an important text is error-free, it might be worth choosing a professional proofreading service instead.

Editing and proofreading are different steps in the process of revising a text.

Editing comes first, and can involve major changes to content, structure and language. The first stages of editing are often done by authors themselves, while a professional editor makes the final improvements to grammar and style (for example, by improving sentence structure and word choice ).

Proofreading is the final stage of checking a text before it is published or shared. It focuses on correcting minor errors and inconsistencies (for example, in punctuation and capitalization ). Proofreaders often also check for formatting issues, especially in print publishing.

The cost of proofreading depends on the type and length of text, the turnaround time, and the level of services required. Most proofreading companies charge per word or page, while freelancers sometimes charge an hourly rate.

For proofreading alone, which involves only basic corrections of typos and formatting mistakes, you might pay as little as $0.01 per word, but in many cases, your text will also require some level of editing , which costs slightly more.

It’s often possible to purchase combined proofreading and editing services and calculate the price in advance based on your requirements.

There are many different routes to becoming a professional proofreader or editor. The necessary qualifications depend on the field – to be an academic or scientific proofreader, for example, you will need at least a university degree in a relevant subject.

For most proofreading jobs, experience and demonstrated skills are more important than specific qualifications. Often your skills will be tested as part of the application process.

To learn practical proofreading skills, you can choose to take a course with a professional organization such as the Society for Editors and Proofreaders . Alternatively, you can apply to companies that offer specialized on-the-job training programmes, such as the Scribbr Academy .

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Literature Review: Purpose of a Literature Review

• Literature Review
• Purpose of a Literature Review
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• Types of Literature Reviews
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The purpose of a literature review is to:

• Provide a foundation of knowledge on a topic
• Identify areas of prior scholarship to prevent duplication and give credit to other researchers
• Identify inconstancies: gaps in research, conflicts in previous studies, open questions left from other research
• Identify the need for additional research (justifying your research)
• Identify the relationship of works in the context of their contribution to the topic and other works
• Place your own research within the context of existing literature, making a case for why further study is needed.

Videos & Tutorials

VIDEO: What is the role of a literature review in research? What's it mean to "review" the literature? Get the big picture of what to expect as part of the process. This video is published under a Creative Commons 3.0 BY-NC-SA US license. License, credits, and contact information can be found here: https://www.lib.ncsu.edu/tutorials/litreview/

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Research on research? If you find this idea rather peculiar, know that nowadays, with the huge amount of information produced daily all around the world, it is becoming more and more difficult to keep up to date with all of it. In addition to the sheer amount of research, there is also its origin. We are witnessing the economic and intellectual emergence of countries like China, Brazil, Turkey, and United Arab Emirates, for example, that are producing scholarly literature in their own languages. So, apart from the effort of gathering information, there must also be translators prepared to unify all of it in a single language to be the object of the literature survey. At Elsevier, our team of translators is ready to support researchers by delivering high-quality scientific translations , in several languages, to serve their research – no matter the topic.

What is a literature review?

A literature review is a study – or, more accurately, a survey – involving scholarly material, with the aim to discuss published information about a specific topic or research question. Therefore, to write a literature review, it is compulsory that you are a real expert in the object of study. The results and findings will be published and made available to the public, namely scientists working in the same area of research.

How to Write a Literature Review

First of all, don’t forget that writing a literature review is a great responsibility. It’s a document that is expected to be highly reliable, especially concerning its sources and findings. You have to feel intellectually comfortable in the area of study and highly proficient in the target language; misconceptions and errors do not have a place in a document as important as a literature review. In fact, you might want to consider text editing services, like those offered at Elsevier, to make sure your literature is following the highest standards of text quality. You want to make sure your literature review is memorable by its novelty and quality rather than language errors.

Writing a literature review requires expertise but also organization. We cannot teach you about your topic of research, but we can provide a few steps to guide you through conducting a literature review:

• Choose your topic or research question: It should not be too comprehensive or too limited. You have to complete your task within a feasible time frame.
• Set the scope: Define boundaries concerning the number of sources, time frame to be covered, geographical area, etc.
• Decide which databases you will use for your searches: In order to search the best viable sources for your literature review, use highly regarded, comprehensive databases to get a big picture of the literature related to your topic.
• Search, search, and search: Now you’ll start to investigate the research on your topic. It’s critical that you keep track of all the sources. Start by looking at research abstracts in detail to see if their respective studies relate to or are useful for your own work. Next, search for bibliographies and references that can help you broaden your list of resources. Choose the most relevant literature and remember to keep notes of their bibliographic references to be used later on.
• Review all the literature, appraising carefully it’s content: After reading the study’s abstract, pay attention to the rest of the content of the articles you deem the “most relevant.” Identify methodologies, the most important questions they address, if they are well-designed and executed, and if they are cited enough, etc.

If it’s the first time you’ve published a literature review, note that it is important to follow a special structure. Just like in a thesis, for example, it is expected that you have an introduction – giving the general idea of the central topic and organizational pattern – a body – which contains the actual discussion of the sources – and finally the conclusion or recommendations – where you bring forward whatever you have drawn from the reviewed literature. The conclusion may even suggest there are no agreeable findings and that the discussion should be continued.

Why are literature reviews important?

Literature reviews constantly feed new research, that constantly feeds literature reviews…and we could go on and on. The fact is, one acts like a force over the other and this is what makes science, as a global discipline, constantly develop and evolve. As a scientist, writing a literature review can be very beneficial to your career, and set you apart from the expert elite in your field of interest. But it also can be an overwhelming task, so don’t hesitate in contacting Elsevier for text editing services, either for profound edition or just a last revision. We guarantee the very highest standards. You can also save time by letting us suggest and make the necessary amendments to your manuscript, so that it fits the structural pattern of a literature review. Who knows how many worldwide researchers you will impact with your next perfectly written literature review.

Know more: How to Find a Gap in Research .

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Why Is Literature Review Important? (3 Benefits Explained)

by  Antony W

January 21, 2023

Every research project needs a literature review. And while it’s one of the most challenging parts of the assignment, in part because of the intensity of the research involved, it’s by far the most important section of a research paper.

Many students fail to write comprehensive literature reviews because they see the assignment as a formality.

For the most part, they’ll vaguely create a list of existing studies and consider the assignment complete. But such an approach overlooks why a literature review is important.

We need to take a step back and look beyond the definition of a literature review.

In particular, the goal of this guide is to help you explore the significance of the review of the existing literature.

Once you understand the role that literature reviews play in research projects, you’ll give the assignment the full attention that it deserves.

Key Takeaways

Writing a literature review is important for the following reasons:

• It demonstrates that you understand the issue you’re investigating.
• A literature review allows you to develop a more theoretical framework for your research. 
• It justifies your research and shows the gaps present in the current literature.

Get Literature Review Writing Help

Do you find the workload involved in writing a literature review for your thesis, research paper, or standalone project overwhelming? We understand how involving the writing process can be, and we are here to help you with writing if you currently feel stuck.

You can hire a  professional literature review writer   from Help for Assessment to get the writing done for you. Whether you have a flexible deadline or the submission date for the literature is almost due, you can count on our team to help you get the paper done fast. 

What is a Literature Review?

A literature review is a study of the already existing research in a given area of study.

While it’s common in physical and social sciences, instructors may also request student to complete the assignment within the humanities space.

The review can be a standalone project or a part of an academic assignment.

If your professor or instructor asks you to write the review as a standalone project, your focus will be on exploring how a specific field of inquiry has developed over the course of time.

In the case where you have to include the review as part of your academic paper, the goal will be to set the background for the topic (or issue) you’re currently investigating.

How is Literature Review Different from an Essay?

In an education setting whether students are used to writing tons of essays every month, it’s likely for many to wonder whether an essay could be the same as a literature review.

While a literature review and an essay both require research before writing, there are a number of differences between them that you need to know.

Types of Literature Review

We’ll look at the significance of a literature review in a moment.

For now let’s look at the types of literature reviews that your instructor may ask you to write.

As of this writing, there are 6 types of reviews that you need to know about. These are:

1. Argumentative Review

Examines a literature review with the intention to support or refuse an argument, with the aim being to develop a body of literature that can establish a contrarian point of view.

2. Integrative Literature Review

This type of review critiques and synthesizes related literature to generate a new framework and perspective on a topic.

Researchers have to address identical and/or related hypotheses or research problems to comply with research standards with regards to replication, vigor, and clarity.

3. Historical Literature

The focus of the review is to examine research within a given period, and usually starts from the time a research problem or issue emerged.

Then, you have to trace its evolution throughout the suggested timeframe within the scholarship of that particular discipline.

4. Methodological Literature Review

The focus shifts from what someone said to how they ended up saying what they said.

Since the focus here is on the method of analysis, methodological reviews gives a better framework that help one to understand exactly how a researcher draws their conclusion from a wide range of knowledge.

5. Systematic Literature

A systematic review focuses on the existing evidence related to a specific research question.

You will need to use a pre-specified and standardized approach to identify, evaluate, and appraise research, not to mention collect, analyze, and report data collected from the review.

Understand that the goal of a systematic review is to evaluate, summarize, and document research that focuses on a specific (or clearly defined) research problem.

6. Theoretical Literature Review

Theoretical review focuses on examining theories that resulted from an issue, a concept, or a situation.

It’s through this type of review that a researcher can easily establish the kind of theories that already formulated, the degree to what researchers have investigated them, and the relationship between them.

It’s through theoretical review that one can develop new hypotheses for testing and can therefore help to determine what theories aren’t sufficient to explain emerging research problems.

Why Is Literature Review Important?

Now that you know the difference between an essay and a review as well as the different types of literature review, it’s important to look at why it’s important to examine existing literature in your research.

There are a number of reasons why instructors ask you to write a review , and they’re as follow:

1. Demonstrate a Clear Understanding of the Subject

Writing a literature review demonstrates that you have a clear understanding of the subject you’re investigating.

It also means that you can easily identify, evaluate, and summarize existing research that’s relevant to your work. 

2. Justify Your Research

There’s more to writing a research paper than just identifying topic and generating your research question from it.

You also have to go as far as to justify your research, and the only way to do that is by including a literature review in your work.

It’s important to understand that looking at past research is the only way to identify gaps that exist in the current literature.

That can go a long way to help fill in the gap by addressing them in your own research work.

3. Helps to Set a Resourceful Theoretical Framework

Because a research paper assignment builds up on the ideas of already existing research, doing a literature review can help you to set a resourceful theoretical framework on which to base your study.

The theoretical framework will include concepts and theories that you will base your research on. And keep in mind that it’s this framework that professors will use to judge the overall quality of your work. 

Frequently Asked Questions

1. what are the benefits of literature review in research.

A literature review in research allows you to discover exiting knowledge in your field and the boundaries and limitations that exists within that field.

Moreover, doing a review of existing literature helps you to understand the theories that drive an area of investigation, making it easy for you to place your research question  into proper context. 

2. What is the Effect of a Good Literature Review?

In addition to providing context, reducing research redundancy, and informing methodology, a well-written literature review can maximize relevance, enhance originality, and ensure professional standards in writing.

3. What is a Strength of a Literature Review?

The strength of a literature review is the ability to improve your information seeking skills and enhancing your knowledge about the topic under investigation.

As you can see, a review is quite a significant part of a research project, so you should treat it with the seriousness that it deserves.

At the end of the day, you want to create a good connection between you and your readers, and the best way to do that is to pack just as much value as you can in your literature review project.

About the author 

Antony W is a professional writer and coach at Help for Assessment. He spends countless hours every day researching and writing great content filled with expert advice on how to write engaging essays, research papers, and assignments.

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Literature review

A general guide on how to conduct and write a literature review.

Please check course or programme information and materials provided by teaching staff, including your project supervisor, for subject-specific guidance.

What is a literature review?

A literature review is a piece of academic writing demonstrating knowledge and understanding of the academic literature on a specific topic placed in context.  A literature review also includes a critical evaluation of the material; this is why it is called a literature review rather than a literature report. It is a process of reviewing the literature, as well as a form of writing.

To illustrate the difference between reporting and reviewing, think about television or film review articles.  These articles include content such as a brief synopsis or the key points of the film or programme plus the critic’s own evaluation.  Similarly the two main objectives of a literature review are firstly the content covering existing research, theories and evidence, and secondly your own critical evaluation and discussion of this content. 

Usually a literature review forms a section or part of a dissertation, research project or long essay.  However, it can also be set and assessed as a standalone piece of work.

What is the purpose of a literature review?

…your task is to build an argument, not a library. Rudestam, K.E. and Newton, R.R. (1992) Surviving your dissertation: A comprehensive guide to content and process. California: Sage, p49.

In a larger piece of written work, such as a dissertation or project, a literature review is usually one of the first tasks carried out after deciding on a topic.  Reading combined with critical analysis can help to refine a topic and frame research questions.  Conducting a literature review establishes your familiarity with and understanding of current research in a particular field before carrying out a new investigation. After doing a literature review, you should know what research has already been done and be able to identify what is unknown within your topic.

When doing and writing a literature review, it is good practice to:

• summarise and analyse previous research and theories;
• identify areas of controversy and contested claims;
• highlight any gaps that may exist in research to date.

Conducting a literature review

Focusing on different aspects of your literature review can be useful to help plan, develop, refine and write it.  You can use and adapt the prompt questions in our worksheet below at different points in the process of researching and writing your review.  These are suggestions to get you thinking and writing.

Developing and refining your literature review (pdf)

Developing and refining your literature review (Word)

Developing and refining your literature review (Word rtf)

Writing a literature review has a lot in common with other assignment tasks.  There is advice on our other pages about thinking critically, reading strategies and academic writing.  Our literature review top tips suggest some specific things you can do to help you submit a successful review.

Literature review top tips (pdf)

Literature review top tips (Word rtf)

Our reading page includes strategies and advice on using books and articles and a notes record sheet grid you can use.

Reading at university

The Academic writing page suggests ways to organise and structure information from a range of sources and how you can develop your argument as you read and write.

Academic writing

The Critical thinking page has advice on how to be a more critical researcher and a form you can use to help you think and break down the stages of developing your argument.

Critical thinking

As with other forms of academic writing, your literature review needs to demonstrate good academic practice by following the Code of Student Conduct and acknowledging the work of others through citing and referencing your sources.  

Good academic practice

As with any writing task, you will need to review, edit and rewrite sections of your literature review.  The Editing and proofreading page includes tips on how to do this and strategies for standing back and thinking about your structure and checking the flow of your argument.

Editing and proofreading

Guidance on literature searching from the University Library

The Academic Support Librarians have developed LibSmart I and II, Learn courses to help you develop and enhance your digital research skills and capabilities; from getting started with the Library to managing data for your dissertation.

Searching using the library’s DiscoverEd tool: DiscoverEd

Finding resources in your subject: Subject guides

The Academic Support Librarians also provide one-to-one appointments to help you develop your research strategies.

1 to 1 support for literature searching and systematic reviews

Advice to help you optimise use of Google Scholar, Google Books and Google for your research and study: Using Google

Managing and curating your references

A referencing management tool can help you to collect and organise and your source material to produce a bibliography or reference list. 

Referencing and reference management

Information Services provide access to Cite them right online which is a guide to the main referencing systems and tells you how to reference just about any source (EASE log-in may be required).

Cite them right

Published study guides

There are a number of scholarship skills books and guides available which can help with writing a literature review.  Our Resource List of study skills guides includes sections on Referencing, Dissertation and project writing and Literature reviews.

Study skills guides

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5 Reasons the Literature Review Is Crucial to Your Paper

3-minute read

• 8th November 2016

People often treat writing the literature review in an academic paper as a formality. Usually, this means simply listing various studies vaguely related to their work and leaving it at that.

But this overlooks how important the literature review is to a well-written experimental report or research paper. As such, we thought we’d take a moment to go over what a literature review should do and why you should give it the attention it deserves.

What Is a Literature Review?

Common in the social and physical sciences, but also sometimes required in the humanities, a literature review is a summary of past research in your subject area.

Sometimes this is a standalone investigation of how an idea or field of inquiry has developed over time. However, more usually it’s the part of an academic paper, thesis or dissertation that sets out the background against which a study takes place.

There are several reasons why we do this.

Reason #1: To Demonstrate Understanding

In a college paper, you can use a literature review to demonstrate your understanding of the subject matter. This means identifying, summarizing and critically assessing past research that is relevant to your own work.

Reason #2: To Justify Your Research

The literature review also plays a big role in justifying your study and setting your research question . This is because examining past research allows you to identify gaps in the literature, which you can then attempt to fill or address with your own work.

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Reason #3: Setting a Theoretical Framework

It can help to think of the literature review as the foundations for your study, since the rest of your work will build upon the ideas and existing research you discuss therein.

A crucial part of this is formulating a theoretical framework , which comprises the concepts and theories that your work is based upon and against which its success will be judged.

Reason #4: Developing a Methodology

Conducting a literature review before beginning research also lets you see how similar studies have been conducted in the past. By examining the strengths and weaknesses of existing research, you can thus make sure you adopt the most appropriate methods, data sources and analytical techniques for your own work.

Reason #5: To Support Your Own Findings

The significance of any results you achieve will depend to some extent on how they compare to those reported in the existing literature. When you come to write up your findings, your literature review will therefore provide a crucial point of reference.

If your results replicate past research, for instance, you can say that your work supports existing theories. If your results are different, though, you’ll need to discuss why and whether the difference is important.

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Perspective article, an urgent call for using real human urine in decentralized sanitation research and advancing protocols for preparing synthetic urine.

• 1 Swedish University of Agricultural Sciences, Department of Energy and Technology, Uppsala, Sweden
• 2 Chemical Engineering Department, University of Cape Town, Cape Town, South Africa
• 3 Future Water Institute, University of Cape Town, Cape Town, South Africa
• 4 Civil Engineering Department, University of Cape Town, Cape Town, South Africa

Recycling resources excreted in human urine can help achieve a sustainable future and circular economy in the sanitation space. However, many studies researching different technologies for safely recycling urine do not use real human urine for experimentation, relying instead on recipes for making synthetic or artificial solutions that attempt to mimic the composition of real human urine. This methodological choice is the focus of this article, which points out that the real urine matrix is extremely complex, with a metabolome (>2,500 metabolites) that differs greatly from that of synthetic urine (<15 metabolites). Therefore, experimental results obtained using synthetic urine can also differ from those obtained using real urine. To exemplify this, we review published literature in terms of four aspects: i) solubility of chemicals and buffering capacity of urine, ii) dissolved organics and membrane fouling, iii) thermodynamic modelling of chemical speciation in urine, and iv) removal of pollutants from urine. We recognise that there is a place for synthetic urine in sanitation research and provide examples of studies where its use is appropriate. Lastly, based on literature from the medical sciences, we provide preliminary guidelines on protocols for preparing synthetic urine that could improve experimentation involving human urine and accelerate the water sector’s transition to circularity.

1 Introduction

In decentralised sanitation systems, human urine can be collected separately from other domestic wastewater and treated to make several useful products, such as water, fertiliser, biostimulants, chemicals and electricity ( Larsen et al., 2013 ). Such recycling has the potential to reduce human transgression of several planetary boundaries, including those on biogeochemical flows of nitrogen and phosphorus ( Perez-Mercado et al., 2022 ; Rockstrom et al., 2023 ). Separate treatment of urine can also benefit existing centralised wastewater treatment plants, e.g. , by decreasing the nitrogen load and thus reducing the energy demand for nitrification ( Wilsenach and Loosdrecht, 2006 ).

Recycling of human urine is a growing research topic within the water sector ( Aliahmad et al., 2022 ). Several novel technologies for treating urine are currently being developed [for recent reviews on this topic, see Larsen et al. ( Larsen et al., 2021 )] and implemented in transdisciplinary initiatives like the Horizon Europe project “P2Green” ( https://p2green.eu/ ) and the Australian Research Council research hub “NiCE” ( https://www.nicehub.org/ ). A growing number of experts believe that decentralised treatment of wastewater could help the water sector accelerate its transition to circularity and that it is well poised to achieve such a paradigm shift ( Guest et al., 2009 ; Larsen et al., 2013 ).

These developments are promising for our own research groups, which are also working in this area. However, a particular trend in current research on decentralised sanitation that gives us cause for concern, and which we address in this article, is the use of synthetic human urine . An analysis of urine research literature, specifically focusing on nutrient recovery, published over the past 5 years, shows an increasing trend in the use of synthetic urine ( Supplementary Material , Supplementary Figure S1 ), with approximately 40% of these studies conducted exclusively with synthetic urine. Of particular concern is that among several publications that exclusively used synthetic urine, 21% referred to the type of urine used as “human urine” in the title of their publications ( Supplementary Material , Supplementary Figure S1 ). For multiple reasons, many studies do not use real human urine in experimental work, and instead rely on recipes for making synthetic solutions that attempt to mimic the composition of real human urine. A simple search of the Scopus database shows that there are hundreds of published articles that have either used synthetic urine for experimentation or have developed assumptions, hypotheses and conclusions based on published studies using synthetic urine. Using synthetic solutions to simulate real fluids is a legitimate scientific method, and one that is not uncommon in wastewater research. In the decentralised sanitation sector, many recipes that can successfully mimic specific physical and chemical properties of human faeces, faecal sludge and greywater have been developed ( Penn et al., 2018 ). In early experimental work, such as proof-of-concept research studies, use of simulants like synthetic urine can help advance science by shedding light on mechanistic aspects of a treatment technology. However, in some instances, using only synthetic urine for experimentation could be problematic from a methodological perspective, especially if protocols for preparing synthetic urine are not well-established and validated by comparison with real urine. To argue why this could be the case, in this article we highlight some of the differences in composition and properties of synthetic urine and real urine. We draw on selected published literature to show how differences between types of urine affect experimental results and their real-life implications. We recognise that there is a place for synthetic/artificial urine in sanitation research and provide examples of cases where its use is appropriate. Our intention is not to criticize studies or researchers that have used synthetic urine in the past. Both of our research groups have also conducted experimental work involving synthetic urine ( Table 1 ). In fact, the observations we made during those studies regarding the differences between real urine and synthetic urine motivated us, in part, to write this perspective article. Overall, we think there is a risk that findings of experiments conducted solely with synthetic urine, especially when prepared using unvalidated protocols, may not be generalisable and transferrable to real-life sanitation systems involving real urine. For instance, studies conducted exclusively using synthetic urine might inadvertently cast a positive light on a urine treatment technology, even if that technology may not prove equally effective when applied to real urine. Therefore, in this perspective article, these authors aim to share with the research community working on decentralised sanitation certain concerns and important considerations when working with synthetic urine. We hope that the article will stimulate a discussion within the research community on the benefits of using real human urine for experimentation work.

TABLE 1 . Concentrations of different constituents in a selection of synthetic fresh human urine recipes described in the literature. Recipes are shown in increasing order of number of metabolites in urine.

2 Real human urine metabolome vs. synthetic human urine metabolome

Urination is the primary route by which the human body eliminates water-soluble wastes. Urine is generated when the kidneys remove water, water-soluble wastes and sugars from the bloodstream. The urine matrix is extremely complex. The major inorganic components of urine include ions such as sodium, potassium, chloride and ammonium, while the major organic metabolites include urea, creatinine, hippuric acid and citric acid ( Putnam, 1971 ; Bouatra et al., 2013 ). Urine also normally contains several other ions, such as calcium, magnesium, phosphate and sulphate, as well as hundreds of metabolic breakdown products from the consumption of food and beverages, the body’s endogenous waste and exogenous compounds such as pharmaceutical drugs or drug metabolites. The human urine metabolome database ( http://www.urinemetabolome.ca ) lists more than 3,000 metabolites or metabolite species that have been detected in human urine using existing analytical methods and technologies, the majority of which are endogenous compounds. As illustrated in Figure 1 , metabolites in real human urine span a wide range of concentrations (nearly 11 orders of magnitude), chemical structures and solubilities (0.0012 g/L for androsterone to 1000 g/L for ethanolamine, according to Bouatra et al. ( Bouatra et al., 2013 )). The concentration of an average metabolite in normal human urine varies by ± 50% ( Bouatra et al., 2013 ), because a wide range of factors, including diet, health, age, gender and activity level, determine the composition of urine ( Rose et al., 2015 ). However, irrespective of the gender or time of the day when it is collected, urine contains more than 90 metabolites with 100% occurrence ( Bouatra et al., 2013 ), but the concentrations always vary. According to Putnam ( Putnam, 1971 ), 68 metabolites contribute >99% of the solutes in human urine. In contrast, synthetic urine recipes in the sanitation field typically contain <15 metabolites ( Table 1 ).

FIGURE 1 . Distribution (%) of organic metabolites measured in real human urine by Putnam ( Putnam, 1971 ) according to their (A) chemical structure and (B) solubility in water at 25°C. Standard solubility definitions were taken from WHO ( WHO, 2022 ).

In published literature on wastewater treatment, it is common to encounter the use of synthetic urine or artificial urine, which is essentially a solution of the major inorganic and organic components in real urine, dissolved in water at room temperature. Table 1 lists a small selection of recipes that have been used in different studies to prepare synthetic urine or are referred to in studies as human urine. While this list is certainly not exhaustive, it clearly shows that there is considerable variation in the choice of inorganic and organic ingredients used for making urine, with some recipes using just one metabolite ( Asiain-Mira et al., 2022 ) and some using up to 11 metabolites ( Wilsenach et al., 2007 ). Urine also has a natural bacterial biome ( Lewis et al., 2013 ) and virome ( Li et al., 2023 ) which is not accounted for by these recipes. Therefore, no synthetic urine recipe, however complex, can ever be truly representative of real human urine.

3 Definitions for different types of urine

It is important to distinguish what type of urine a recipe is attempting to mimic. Fresh urine refers to urine collected immediately after it is excreted, although there is no consensus within the research community on how long after excretion urine can be considered fresh. In the literature, some studies have used freshly excreted urine immediately in experiments ( Flanagan and Randall, 2018 ) or have stored it for a few hours ( Vasiljev et al., 2022 ) or days ( Simha et al., 2018 ; Ray et al., 2020 ) at different temperatures (3°C–30°C) before use. However, in general the term “fresh” is typically used to indicate that no urea hydrolysis has occurred in urine. If fresh urine is diluted with flushwater, it is referred to as diluted fresh urine ( e.g. , see synthetic recipe of Han et al. ( Han et al., 2022 ) in Table 1 ). If fresh urine is treated to inhibit urease-catalysed hydrolysis of urea to ammonia, for instance by acidification ( Simha et al., 2023 ), alkalisation ( Randall et al., 2016 ) or oxidation ( Lv et al., 2020 ), the literature defines it as stabilised fresh urine . If urea hydrolysis is not prevented and the majority of the nitrogen in urine is in the form of ammonia, then the urine is considered to be hydrolysed or ureolysed ( Udert et al., 2003a ). If all the urea excreted in fresh urine is not hydrolysed to ammonia, then the urine is considered to be partially hydrolysed ( Tuantet et al., 2013 ). If hydrolysed urine is treated biologically to stabilise ammonia nitrogen, for instance by nitrification ( Udert and Wachter, 2012 ), then literature defines it as biologically stabilised urine . However, studies using synthetic urine sometimes fail to report what type of urine their recipe represents. Each type of urine has a distinct composition and physical and chemical properties, and distinguishing between the types is important as it has implications for further urine treatment (see, e.g. , Simbeye et al. ( Simbeye et al., 2023 ) for an insight into the effect of type of human urine on recovery of phosphate as vivianite). This is one area where the research community would benefit by working together to develop consistent terminology and best practices for reporting experiments involving human urine.

4 Implications of the differences between synthetic urine and real urine

To highlight some key differences between synthetic urine and real urine and the implications of these differences, we conducted a non-systemic literature review, the results of which are summarised below.

4.1 Solubility of chemicals and buffering capacity of urine

Type of urine matrix affects the solubility of different chemicals and the capacity of urine to buffer changes in pH. For example, fresh urine can be dosed with sparingly soluble alkaline Earth chemicals such as Mg(OH) 2 and Ca(OH) 2 to inhibit urease activity and urea hydrolysis. However, Mg(OH) 2 is 40% less soluble in synthetic urine and, due to lower buffering capacity, also has higher pH (>10.8) after treatment than real urine after treatment (pH < 10.6) ( Simha et al., 2022 ). Studies by Ray et al. ( Ray et al., 2018 ) and Simha et al. (2023) have shown that the acid dose needed to shift the pH of fresh urine to below 3.0 is at least two-fold higher for real urine. These are important observations since the stability of most urine treatment processes relies on accurately dosing chemicals. The operating costs of decentralised sanitation systems can also be significantly affected by the chemical demand for treating urine.

The prevailing pH affects both the solubility and the degradation of different organic metabolites in urine. For instance, the rate of degradation of creatine increases as the pH decreases ( Jager et al., 2011 ). In studies on urine acidification and concentration by reverse osmosis, Courtney and Randall ( Courtney and Randall, 2021b ) have shown that crystals of uric acid dihydrate form in acidified real urine, but not in synthetic urine, resulting in scaling of the membrane surface. These observations are consistent with findings by Wang and Königsberger ( Wang and Königsberger, 1998 ) that the solubility of uric acid decreases as the pH declines and ionic strength of the solution increases. These results suggest that reverse osmosis is not well suited for concentrating acidified urine, while other treatments such as evaporation are not significantly affected by biofouling and scaling. However, apart from three studies on reverse osmosis in the literature (viz. Ek et al. ( Ek et al., 2006 ), Ray et al. ( Ray et al., 2020 ), Courtney and Randall ( Courtney and Randall, 2021b )), to our knowledge other studies have only used synthetic urine for experimentation.

Poorly soluble organic compounds tend to co-precipitate with inorganic compounds in real urine. In a study focusing on precipitation of phosphate from fresh urine as vivianite, Simbeye et al. ( Simbeye et al., 2023 ) showed that relatively pure (95%) vivianite could be produced from synthetic urine, but that the purity of vivianite decreases to 75% when made from real urine. This is because organic metabolites in real urine form complexes with divalent ions such as Fe 2+ and these complexes can grow around vivianite crystals ( Wei et al., 2019 ) and limit its yield and purity. These differences ultimately affect process economics, as further treatment will be required to improve product purity ( e.g ., washing vivianite with solvents to selectively remove organic compounds).

4.2 Dissolved organic compounds and membrane fouling

Many synthetic urine recipes ( Table 1 ) are made up of salts to replicate the major inorganic metabolites in urine. However, real urine also has a high organic component (about 10 g COD L -1 according to ( Udert et al., 2006 ) or approximately 25% of the total dissolved solids estimated by Putnam ( Putnam, 1971 )). A research area where the missing organics in synthetic urine leads to significantly differing experimental results is in membrane research (reverse osmosis, nanofiltration, membrane distillation, etc.), specifically with regards to membrane fouling. For example, during membrane distillation, a crystalline deposit forms on the membrane when synthetic urine is used, while with real urine the deposit that forms is more complex and composed of a rich organic fraction ( Kamranvand et al., 2018 ). Bacteria ( Crane et al., 2022 ) and a combination of urinary sugars and protein ( Guizani et al., 2016 ) have been shown to cause membrane fouling when urine is concentrated by forward osmosis. Zhang et al. ( Zhang et al., 2023 ) found that fouling of a hollow fibre membrane contactor for treating real hydrolysed urine increases as the pH of urine decreases.

The solubility ( Franks et al., 2024 ) and the charge ( Wen-Qiong et al., 2019 ) of organic compounds are both affected by pH. If the charge on the membrane is the same as the charge on an organic compound, electrostatic repulsion between the organic compound and the membrane pores will increase, thus reducing the potential for fouling ( Van Reis et al., 1997 ). Higher solubility means that a higher urine concentration factor can be achieved during treatment before organic compounds precipitate. The properties of the feed solution (pH, ionic strength) and the membrane (charge, hydrophobicity, roughness) affect thermodynamic interactions between dissolved organic compounds and the membrane surface, and influence the mechanisms that cause fouling ( Tang et al., 2011 ).

Experimental results obtained when treating real urine are not always inferior to those obtained when treating synthetic urine. Studies by Courtney and Randall ( Courtney and Randall, 2021b ) and Pronk et al. ( Pronk et al., 2006 ) observed increased rejection of urea during membrane treatment of real urine. Courtney and Randall ( Courtney and Randall, 2021b ) found that improved rejection of urea increased overall urea recovery from 79.2% to 85.5% when comparing synthetic urine and real urine. Pronk et al. ( Pronk et al., 2006 ) attributed the increase in rejection of uncharged molecules such as urea to complexation of compounds with the organic substances in real urine. There is also evidence that urea promotes protein unfolding by directly interacting with polar moieties of proteins via hydrogen bonding ( Bennion and Daggett, 2003 ). Unfortunately, synthetic urine cannot be improved by merely adding organics to the recipe used, as in many of these cases the exact organic compounds causing the fouling have not yet been identified (only that they are organic is known) ( Courtney and Randall, 2021b ; Crane et al., 2022 ). In these cases, using both real and synthetic urine for experiments becomes valuable for comparing fouling (or lack thereof).

4.3 Thermodynamic modelling of chemical speciation in urine

All models used to simulate a process in urine essentially model synthetic urine. As with making synthetic urine, it is challenging to include every metabolite excreted in real urine in a thermodynamic model. Many modelling databases do not include a comprehensive list of urinary metabolites. For example, the chemistry database of the thermodynamic modelling software OLI ( OLI Systems and Inc, 2020 ) does not include major organic metabolites excreted in urine, such as creatine, creatinine and uric acid. The importance of including or excluding a metabolite will depend on the parameter being measured/simulated. Udert et al. ( Udert et al., 2003b ) developed a model using Aquasim to estimate the potential for mineral precipitation in sanitation systems that separately collect human urine and found good agreement between simulated and experimental results when the degree of dilution of urine by flushwater was accurately accounted for. Courtney et al. ( Courtney et al., 2021 ) used the same thermodynamic model (in Aquasim) to simulate removal of calcium from human urine by air and CO 2 bubbling and found that initially the model did not accurately simulate the pH of urine as a function of bubbling duration. They attributed this to the salinity of urine influencing the pK a of HCO 3 − /CO 3 −2 ( Millero et al., 2006 ) and to inclusion of creatinine in the model affecting the buffering capacity of urine at pH 9.2. When adjusted for these two factors, the model accurately captured the change in pH of urine during bubbling ( Courtney et al., 2021 ). Inaccurate simulation of chemical speciation in urine and using synthetic human urine with only a few metabolites therefore have implications for the design of experiments and treatment processes ( e.g ., operating conditions such as pH and temperature), and for analysis of experimental results ( e.g ., when evaluating the form and fate of plant-essential nutrients excreted in urine after treatment).

4.4 Removal of pollutants from urine

Several previous studies have used synthetic urine to evaluate removal of pollutants that can potentially be excreted in urine, such as residues and metabolites of pharmaceutical drugs, pesticides, hormones, personal care products, chemicals used for cleaning toilets and heavy metals ( Landry et al., 2015 ; Sun et al., 2018 ; Almuntashiri et al., 2022 ; Goulart et al., 2022 ; Rodriguez et al., 2022 ; Yao et al., 2022 ). Many of these are presented as proof-of-concept studies, and there are often no follow-up studies to evaluate whether the treatments can be replicated with a real urine matrix. In some follow-up studies, clear and significant deviations have been observed between studies, primarily because of differences between the urine matrices. There is evidence that analytical detection of pollutants is significantly affected by the type of matrix studied. For instance, ionisation of the target analytes in LC-MS/MS can be affected by endogenous compounds present in urine ( Rossmann et al., 2015 ). The matrix can also affect the removal efficiency of pollutants because the physical and chemical properties of real urine are different from those of synthetic urine, and no synthetic recipe has been developed to account for the hundreds of endogenous organic metabolites excreted in urine ( Figure 1 ). For example, Solanki and Boyer ( Solanki and Boyer, 2017 ) found that >90% removal of pharmaceuticals from synthetic urine could be achieved by adsorption onto biochar. However, in follow-up studies involving real urine, they found that removal of pharmaceuticals declined to 40% because of competition for adsorption sites by dissolved organic compounds naturally excreted in urine, such as urobilin ( Solanki and Boyer, 2019 ). In a study evaluating degradation of 75 organic micropollutants (OMPs) by a UV-based advanced oxidation process, Demissie et al. ( Demissie et al., 2023a ) observed average ΣOMP degradation of 99% (±4%) in Milli-Q water, but only 55% (±36%) in real fresh urine. This is because endogenous organic compounds in urine can competitively absorb UV light (creatinine and amino acids have high UV absorbability according to Yokoyama et al. ( Yokoyama et al., 2005 )) and can scavenge free radicals. In another study, Demissie et al. ( Demissie et al., 2023b ) found that the UV dose needed to irreversibly denature jack bean ( Canavalia ensiformis ) urease (EC 3.5.1.5) in real fresh human urine was 25-fold higher than the dose needed to denature urease in synthetic fresh human urine. Unfortunately, there seems to be more literature available on treatment of synthetic human urine than on treatment of real human urine for removal of contaminants such as micropollutants.

5 Why and when to use synthetic urine for experimentation?

While synthetic urine is not exactly representative of real urine, it does have many uses and benefits. Below we list a few valid reasons why synthetic urine may be used in research:

1. The composition of real urine varies considerably, as it is influenced by diet, health, age, gender, activity level of people and other factors ( Rose et al., 2015 ). The composition of synthetic urine can be fixed, which can be desirable when conducting experiments to evaluate the influence of several operating conditions on treatment objectives ( Tarpeh et al., 2018 ). The experimental results obtained when synthetic urine is used are generally more consistent than results obtained using real urine with varying composition ( Kabdaşlı et al., 2022 ).

2. The use of synthetic urine is appropriate in proof-of-concept research that proposes novel technologies and methods to treat urine, e.g. , Arve and Popat ( Arve and Popat, 2021 ). If experimentation using synthetic urine yields undesirable results, then further testing can be avoided, and time and resources can be saved. For instance, Ray et al. ( Ray et al., 2018 ) showed that zinc and silver ions are not effective inhibitors of urease in synthetic fresh urine as they precipitate with phosphate and chloride naturally present in urine, although the inhibition of urease in soil by these heavy metal ions is well established.

3. Using a synthetic recipe makes it easier to reverse-engineer processes and identify metabolites or properties of urine that significantly affect the outcome of a treatment ( Solanki and Boyer, 2019 ). In addition, different technologies can be more fairly compared against each other if the same synthetic urine recipe is used to evaluate their differences ( Chen et al., 2023 ).

4. Synthetic urine can be helpful for developing new analytical methods for targeted analysis of metabolites ( Scherr and Sarmah, 2011 ) and for educational purposes where the aim is to train students in analytical chemistry or wastewater engineering.

5. Computer-based thermodynamic models of chemical speciation must be validated in real experiments ( Courtney and Randall, 2023 ). Synthetic urine is particularly helpful in such cases since it is not always possible to conduct a full metabolomic analysis of real urine. Many metabolites also do not exist in the chemistry databases of software tools.

6 Guidelines on protocols for preparing synthetic fresh human urine

As shown in Table 1 , several recipes for preparing synthetic human urine are found in the water and sanitation literature. However, to the best of our knowledge, none of these recipes use well-established protocols for preparing synthetic urine, ( Lienert and Larsen, 2009 ; Jewitt, 2011 ; Furlong et al., 2019 ; Simha et al., 2021 ), nor have they been validated by comparison with real urine specimens. On the other hand, there is extensive literature in the medical sciences focusing on the development of protocols for synthetic urine preparation in various research domains, including urology ( Shafat et al., 2013 ), dermatology ( Mayrovitz and Sims, 2001 ) and nephrology ( Brooks and Keevil, 1997 ). These protocols have typically been designed to allow investigation of specific aspects, such as the formation of kidney stones ( e.g. , calcium oxalate dihydrate) in urine, study of renal physiology using in vitro cell culture ( Chutipongtanate and Thongboonkerd, 2010 ), urinary tract infections and growth of urinary pathogens ( Brooks and Keevil, 1997 ). More recent efforts have developed protocols for synthetic urine preparation that are not specific to an application, ( Chutipongtanate and Thongboonkerd, 2010 ; Sarigul et al., 2019 ), and can be more universally used across research disciplines ( Table 2 ). In fact, Sarigul et al. (2019) have shown that, by using attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), their synthetic urine comes closest to mimicking real urine. This recipe differs from many of those presented in Table 1 in two ways. First, it does not just include major inorganic metabolites and urea, but also major organic metabolites like creatinine, uric acid, citrate, and oxalate, which are normally excreted in real urine. Secondly, the recipe adds both NaH 2 PO 4 ·2H 2 O and Na 2 HPO 4 ·2H 2 O which more accurately reflects the speciation of phosphate in real fresh urine, which eliminates the need for adding HCl or NaOH to adjust the pH of urine. Their protocol is also practical as it does not contain an unreasonable number of metabolites (<15). Therefore, to urine researchers working in the sanitation space, we recommend using the protocol developed by Sarigul, et al. ( Sarigul et al., 2019 ) for preparing synthetic urine. However, considering that the concentration of different metabolites in urine varies (e.g., between 9.3 and 23.3 g L -1 for urea according to Putnam ( Putnam, 1971 )), we also suggest researchers to adjust the protocol (as shown by the “adjusted Putnam” recipe in Table 2 ) to prepare synthetic urine that accurately represents real urine produced in various geographical contexts. The key components of any synthetic urine recipe should include all major inorganic ions (Na + , K + , Mg 2+ , Ca 2+ , NH 4 + , Cl − , SO 4 2- , PO 4 -P), and all major organic metabolites (urea, creatinine, uric acid, citrate, and oxalic acid).

TABLE 2 . Concentrations of different constituents in a selection of synthetic human urine recipes described in the medical sciences literature. To urine researchers working in the sanitation space, we recommend using the protocol developed by ( Sarigul et al., 2019 ) and adapt it to account for variation in concentration of different metabolites excreted in urine. “Putnam adapted” shows the minimum and maximum acceptable limits for concentration of major metabolites in urine.

There are several sub-topics in sanitation-focused urine research, including the recovery of plant-essential nutrients and energy, removal of micropollutants, and inactivation of pathogens. These would need to be considered when adapting and using such a protocol. It is always possible to add more metabolites to synthetic urine depending on the question at hand (e.g., Brooks and Keevil ( Brooks and Keevil, 1997 ) added bacteriological peptone to account for amino acids and short chain peptides and yeast extract to account for nucleic acids excreted in urine, respectively). This can be particularly relevant when experimentation involves developing methods to reduce malodour from urine-separating toilets or light irradiation to degrade pollutants in urine, as all protocols for making synthetic urine produce odourless and colourless urine.

7 Conclusion and the way forward

Research on innovative technologies to recycle the resources in human urine is highly relevant for achieving a sustainable future and circular economy in the sanitation space. As such research has real-life implications, it is critical to constantly evaluate methods and methodological choices used in experimentation on this topic. One such choice that researchers must make is whether to use synthetic urine or real human urine. In this article, we argue that it can be difficult to accurately replicate the complex metabolome and properties of real urine using a synthetic recipe. We provide select examples from literature to suggest that results obtained when synthetic urine is used can differ from those obtained when real urine is used. In some cases, results of experiments conducted with real urine are not as promising as those achieved with synthetic urine, but publication of negative results is still to the benefit of the entire research community. While there are several benefits and valid reasons for using synthetic urine in research, some of which we present in this article, we have also noted a lack of consistency in the protocols for preparing synthetic urine in sanitation research. To address this, we provide suggestions and preliminary guidelines on protocols for preparing and using artificial urine, inspired by literature from the medical sciences. We hope that this article initiates a discussion on methodological choices in urine research among the community engaged with decentralised sanitation systems. Overall, we have the following recommendations:

1. Whenever it is feasible, work with real urine. Urine can be collected in a depersonalised manner from several donors and pooled together. Increasing the number of donors or the collection period for urine can mitigate issues related to variability in urine composition.

2. When preparing synthetic urine, use protocols that have been evaluated and validated with real urine, such as the protocol outlined by ( Sarigul et al., 2019 ) (See Table 2 ). Modify the protocol as shown in “Putnam adapted” in Table 2 to make synthetic urine that is representative of real urine produced in various geographical contexts. Include or exclude specific metabolites from the protocol depending on the research question, as this can be important when assessing different topics in sanitation-focused urine research, such as the degradation of micropollutants.

3. Follow up an experiment involving synthetic urine that yielded positive results with an experiment using real human urine, ideally within the same study. In studies where results of only synthetic urine are reported, authors should try to hypothesize how their results could differ in case real urine is used, raise any potential aspects that could be of concern, and recommend follow-up studies to use real urine to validate these hypotheses and/or confirm that similar results with real urine can be achieved.

4. Always clearly state in the article title, abstract and conclusions whether real or synthetic/artificial urine was used in experiments. In addition, specify within the article the type of urine used/replicated in the study (see Section 3 for definitions).

5. Work together as a community to develop terminology, definitions, methodologies and best practices for experimental work involving human urine.

Data availability statement

The original contributions presented in the study are included in the article/ Supplementary Material , further inquiries can be directed to the corresponding author.

Author contributions

PS: Conceptualization, Data curation, Formal Analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Validation, Visualization, Writing–original draft, Writing–review and editing. CC: Conceptualization, Data curation, Formal Analysis, Investigation, Methodology, Software, Validation, Visualization, Writing–original draft, Writing–review and editing. DR: Conceptualization, Investigation, Methodology, Software, Writing–original draft, Writing–review and editing.

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. PS was supported by grants from Stiftelsen Lantbruksforskning for the project “Micropollutants-free sustainable beer production” (Grant number O-22-23-744) and the European Union’s Horizon Europe Research and Innovation Programme for the project “P2Green: Closing the gap between fork and farm for circular nutrient flows” (Grant number 101081883). Dyllon Randall and CC were supported by internal funding from the University of Cape Town and the August T Larsson Guest Researcher Programme at the Swedish University of Agricultural Sciences.

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fenvs.2024.1367982/full#supplementary-material

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Keywords: simulation, synthetic urine, membrane, micropollutants, nutrient recycling, wastewater treatment

Citation: Simha P, Courtney C and Randall DG (2024) An urgent call for using real human urine in decentralized sanitation research and advancing protocols for preparing synthetic urine. Front. Environ. Sci. 12:1367982. doi: 10.3389/fenvs.2024.1367982

Received: 09 January 2024; Accepted: 04 March 2024; Published: 14 March 2024.

Reviewed by:

Copyright © 2024 Simha, Courtney and Randall. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Prithvi Simha, [email protected]

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Making literature reviews more ethical: a researcher and health sciences librarian collaborative process

Bejoy thomas.

1 Department of Psychosocial & Rehabilitation Oncology, Tom Baker Cancer Centre, CancerContol Alberta, Alberta Health Services, Calgary, AB, T2S 3CI, Canada

2 Department of Oncology, Cumming School of Medicine, University of Calgary, Calgary, AB, T2N 1N4, Canada

Admasu Tachble

Delshani peiris, rebecca malhi, glenys godlovitch.

3 Alberta Cancer Research Ethics Committee, CancerContol Alberta, Alberta Health Services, Calgary, AB, T2N 1N4, Canada

Yongtao Lin

4 Knowledge Resource Service, Knowledge Management Department, Tom Baker Cancer Centre, University of Calgary, Calgary, AB, T2N 1N4, Canada

Background:

With emphasis on evidence-based medical care, ‘evidence’ is often the result of literature reviews. Hence, the critical question, “are literature reviews comprehensive?”

This study compares the literature generated by a researcher and a health sciences librarian (HSL).

The Research Associate and the HSL conducted a parallel, segregated literature search on ‘patient-centered care’.

The Research Associate identified 215 manuscripts, and the HSL 129 manuscripts. Overlap was only 55 manuscripts. Differences in process and blind spots are discussed.

Conclusion:

To improve the quality of research outcomes, it seems prudent and ethical to have a synergistic collaboration between researchers and HSLs. Given that this is just one case study that has looked into the issue, further research is strongly encouraged.

Lay abstract: Literature reviews are not just compilations of easily accessible research and should not be taken lightly. Literature reviews are critical to decision-making in clinical trials, medical care and directions of health systems. We wanted to see if researchers and health science librarians working in isolation would create a robust and balanced literature review. This case study showed that both approaches have shortcomings. We recommend that researcher and health science librarian must work together for the success of improving medical care.

Research is cumulative in nature, building on prior studies on the topic of interest. Thus, it is important for the researcher to have robust understanding of the extant knowledge. A comprehensive literature review will describe the research concepts, ground critical appraisal of previously published studies and identify gaps or inconsistencies in the knowledge base, which merit further investigation. Reviewing the literature requires several skills, and is usually done in one of two ways. In the first approach, the researcher (or the research team) critically evaluates relevant information and effectively scans the literature for both breadth and depth of information, to the best of their ability [ 1 ]. Consequently, the researcher/team's capacity to locate and access appropriate studies influences the quality of the research reviewed [ 2 ].

The second option is to engage the services of a health sciences librarian (HSL) with in-depth knowledge of various evidence resources and the professional training to conduct comprehensive literature searches. The comparative advantage researchers have by working with a HSL in the research process is well documented [ 3–7 ]. Yet, the librarian often tends to have a subordinate role and the partnership could be summarized as ‘we (the researcher) gave them the key words, they had a few questions for us, and a week later we got the reference list’. Can the literature review process be optimized? In this case report, we compare the results of literature reviews conducted by a researcher and a HSL.

Review teams

Two separate teams were created for the literature search with a principal investigator (PI) taking the role of independent subject expert in each. One team was comprised of a PhD-trained research associate (RA; A Tachble) and the PI (B Thomas). The other team was comprised of the HSL (Master of Library Information Sciences; Y Lin) and the PI. The PI facilitated the process but did not share information between groups. Thus, both teams conducted parallel, segregated literature searches on the same topic.

Literature review procedure

The literature review process was conducted in four steps: determine the topic of interest; define inclusion and exclusion criteria; compile the literature (total hits); and evaluate the literature to determine ‘relevant hits’ by relevance of the identified literature to the topic of interest (e.g., use of token keyword); a predefined context or setting ; the nature of each hit – is it original (clinical) research or a theoretical stance; and if the original research's methodology could facilitate a decision process to clinical practice (i.e., is process A better than, or equivalent or cost effective, among others compared with process B?)

In the first step, we determined the existing background information on the chosen topic – ‘patient-centered care’ – and began a broad-scale search to identify concepts and to create a provisional list of keywords: patient-centered care, family-centered care, cancer, malignant neoplasm, chronic disease(s), tertiary care, rural care and healthcare provider. For step two, we defined the inclusion criteria (articles published during 2000 and onwards, English language and print/electronic media access to full text, among others) and exclusion criteria (non-English language, personal communications, nonelectronic materials, publications dated prior to 2000 and pediatric/pediatric population) for the literature. The PI then provided these to the RA and the librarian.

The literature search (the third step) included searching through electronic research databases, conference proceedings, dissertation abstracts among others to identify published articles, reports and works in progress. Both teams accessed Cochrane, PsycInfo and MEDLINE data sources to locate published studies/literature addressing patient-centered care. In addition to these, the librarian also searched EMBASE, EBSCO Business Source Complete and Cumulative Index to Nursing and Allied Health Literature (CINAHL), ProQuest Dissertations and Thesis and Web of Science. The RA accessed PubMed and Google Scholar as well.

The literature reviews were evaluated and scored using the following metric:

• Relevance of the identified literature to the topic of patient or family centeredness (10 points);
• Context or setting: cancer (10 points) or chronic disease(s) (5 points);
• Nature of manuscript: original research (e.g., clinical practice; 10 points) or theoretical concept (literature review, hypothesis among others)? (5 points);
• If the study had an evaluation component and/or used a study design to differentiate between study groups (5 points, respectively) in the manuscript.

The RA and the PI completed the shortlisted manuscript scoring for both teams. A cutoff score for relevance was set at 20 points.

Results are displayed in Figure 1 . The RA obtained 1275 total hits with 215 manuscripts meeting the cutoff score for relevance. The librarian obtained 1232 hits, with 184 manuscripts meeting the relevant scoring criteria. Among the relevant manuscripts, there was a general overlap of 55 (16% of final literature capture) manuscripts between the two teams. The total unique literature capture was 344 manuscripts. The librarian's unique contribution to this literature capture (excluding the general overlap) was 129 manuscripts (37.5% of the final literature capture). Similarly, the unique contribution of the RA was 160 manuscripts (46.5%).

HSL: Health science librarian; PI: Principal investigator.

In this case study, we note two intertwined but critical aspects. First, the literature capture process by a researcher is a function of their training and experience. The hits obtained here are therefore unique to this researcher (A Tachble); other researchers may have higher or lower hit rates. This leads us to the process resulting in this variance. The librarian worked from the key words and used possible subject headings, related keywords and synonyms to refine a search process. Given that librarians are well acquainted with the anatomy of literature, they work from a very algorithmic process of deductive steps – from creating a very large catchment area, and reducing it by incorporating the exclusion criteria, and honing in on the critical mass by utilizing the inclusion criteria, to subject heading or other control vocabularies. This process of using documented search strategies is replicable between most librarians. Even a few researchers possibly follow these steps. Yet, we believe that most researchers will use databases to create citation lists – particularly databases like PubMed and Google Scholar. This is in essence browsing and utilizes snowballing techniques like perusing through the bibliography of identified hits. Interestingly, searching the term ‘Google Scholar’ in PubMed retrieves about 3926 results, as of August 2015. It would also seem that the 768 + 122 unique hits obtained by the researcher is a result of snowballing and being able to review its content as opposed to capturing it algorithmically; in other words, the manuscript may not be accurately represented by keywords and by extension of medical subject headings (MeSH) and other indexed terms.

The second important interrelated aspect we raise is time utilized by the researcher to compile the literature search. In this case study, the researcher took about 4 weeks to compile 1275 hits. Not all researchers have the luxury of an extended period of time to undertake a comprehensive literature review alone [ 8 ]. In contrast, the librarian would normally take 1–2 days to create and run algorithms, scan the results and rerun the algorithms with a few tweaks to improve or fine-tune the results.

We therefore contend that a literature review by a researcher alone may not be comprehensive using methods of browsing and snowballing. This is quite obvious in Figure 1 where 49 manuscripts that were identified by both teams were not included in the researchers’ final list, primarily because the full manuscript/source document could not be identified. Although their training in resource identification and retrieval is indispensable [ 9–11 ], the expectation that the literature search being the HSL's sole responsibility is – in our opinion – flawed. Our case study seems to indicate that in order to accomplish a literature search with due diligence, a deliberate researcher–HSL collaboration is necessary. Perhaps working in isolation from each other, then collating their findings could be a ‘best practice’ that produces a robust and comprehensive knowledge set.

Even though this is a single case study, and further research is strongly encouraged, from an ethics perspective, these results have important implications for clinical and institutional practices. Patients place their trust in clinicians to provide expert advice and care and in healthcare institutions to facilitate the delivery of good clinical practice through sound, well-informed guidelines. Clinical teams and institutions are legally and ethically bound to provide care that is partly knowledge-based, partly policy-based and partly skills-based. Each of these aspects has its relevant standard that is to be matched or surpassed by competent practitioners. The imperatives of evidence-based medicine are to: ensure that clinicians are aware of what would provide their patient populations with the best care and interventions possible, and inform institutional policy-makers about the relevant options in determining policy. Our findings suggest that the quality of the literature review yielded by the researcher–HSL partnership would satisfy these imperatives.

There are systemic implications too. One is with respect to informing development of clinical guidelines. The presentation of incomplete information may tend to generate an underinformed practice guideline that if implemented could result in causing avoidable harms (or perhaps even in misunderstood benefits). Another systemic implication is that by placing reliance on one form of literature review over the other, the direction of future research could become skewed. As the differences between results for the two searches show, literature blind spots arise. An author is not well placed to be able to report his or her own blind spots, but once published in a peer-reviewed forum, the article or report takes on a certain authority and lives a life of its own in future literature reviews. Any one viewpoint can only tell the story from its own perspective even when done with the good intention of generating evidence-based guidance for actual clinical decision-making. With this in mind, the advantage of having a multiple expertise-enriched literature review is obvious.

Conclusion & future perspective

The results of this single case study demonstrate the advantages that researchers could have by not only involving professional librarians but also by becoming active participants in the literature search endeavor. The ethical implication of the absence of this process is large given the blind spots in the current way of doing literature reviews. For quality control purposes, we believe that that journal editors and peer-reviewers should have a checklist or a process in place to ensure that due diligence in the literature review has been done on any new submission.

Executive summary

• A comprehensive literature review is the cornerstone of any scientific research endeavor.
• Literature reviews are usually conducted by a researcher/team or by a health sciences librarian (HSL).
• The literature capture processes used by researchers and HSLs working in isolation from each other – ‘browsing’ versus ‘algorithmic searching’ – are different, and both lead to blind spots.
• To accomplish due diligence in a literature search – which has ethical and systemic implications – a deliberate researcher–HSL collaboration is necessary.

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.

Informed consent disclosure

The authors state that they have obtained verbal and written informed consent from the patient/patients for the inclusion of their medical and treatment history within this case report.

Open access

This work is licensed under the Creative Commons Attribution 4.0 License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/