Medical Literature Reviews are a core part of medical research and evidence-based medicine. There are so many journal articles out there, it would be impossible to stay current with the literature. Thankfully there are many literature reviews published on virtually every subject in medicine.

Many students and researchers conduct or write a literature review as part of their education into understanding how to critically appraise medical research. It is a very useful exercise but it can also be an incredibly daunting one. In this article, I hope to pass on some useful advice on how to conduct a literature review.

I would like to acknowledge Marco Pautasso (1) from whom a great deal of the information presented in this article was gathered. He has written a great article on how to write a literature review which is available for free from PMC.

Updated 22nd May 2021

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What is a Literature Review?

A literature review is a type of research study that aims to critically discuss research that has previously been published. Literature reviews can lead to new insights and highlight gaps and disagreements in current knowledge.

When someone has finished reading your literature review, they should have a clearer understanding of:

• The major achievements in the area of research being reviewed
• The main causes for debate or disagreement
• The gaps in current knowledge

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10 Simple Rules for a Literature Review

1. Define a Topic and an Audience
2. Search and Re-Search the Literature
3. Take Notes While Reading
4. Choose the Type of Review You Wish to Write (mini vs full review, descriptive vs integrative review, narrative vs systematic review/ meta-analysis)
5. Keep the Review Focused (but Make it of Broad Interest)
6. Be Critical and Consistent
7. Find a Logical Structure
8. Make Use of Feedback
9. Include Your Own Relevant Research (but Remain Objective)
10. Make Your Review Up-to-Date (but Don’t Exclude Older Studies)

Adapted from Marco Pautasso (1)

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Skills involved in Reviewing Literature

• Ability to find and evaluate relevant information
• Ability to summarise information succinctly
• Critical Analysis
• Communication and Writing Skills
• Paraphrasing
• Citation Management

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How to Start a Literature Review?

First of all, you must choose a topic for your literature review. This topic should be:

1. Interesting (something you want to write about)
2. Important (so other people will want to read it and so you will be able to find enough existing literature on the subject)
3. Focussed

How to actually choose is a different matter. You should consider the problems that you observe in your current area of interest or practice. Try to use the literature review to learn more about that problem and form your own opinions on it.

You could also consider suggestions for reviews from general websites, your lecturer or senior colleagues and other research papers already published in your area.

Whatever you choose, you need to make sure you formulate a focused research question. Define the scope of your literature review and decide on inclusion and exclusion criteria for your literature search.

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How to Conduct a Literature Search?

This is a very brief overview of how to search the literature. Searching the literature involves three phases.

Phase 1: This is where you do a rough search of the literature. Use any resource or database you like and enter keywords relating to your subject matter.

Read some articles and get a sense of the overall themes and words used related to your topic.

Compile a list of keywords or search terms that you can use later.

Phase 2: Now you will conduct your comprehensive and systematic search of the literature.

You need to group your keywords by concept and go to the Advanced Search option for the database that you are using.

Conduct a search using all of the keywords in each concept. These keywords need to be separated by the “OR” command. Don’t forget to include MESH terms and *wildcard features.

Once you have completed the search for each concept you will conduct a new search using the “AND” function between each of your concept searches.

Then limit your search using the various filters if you only want articles published in English or Publication Date for example.

Phase 3: Finally, try to narrow down your search results to include only relevant articles. You need to develop some exclusion criteria that you will disclose in your Methods section of the Literature Review. You could first remove articles with a clearly irrelevant title. Then remove articles by irrelevant abstract. Then remove articles if they are truly inaccessible. Finally, you will need to read the full text to determine if a paper should be included in your Literature Review or not.

Additionally, you may find articles that should be included in your review that were cited by your included papers but not found in your search. You should include these papers as well.

If you are using more than one database to find papers, then I recommend downloading the included files into a citation manager so that you can easily identify and count your duplicates.

All of this needs to be outlined in a flow diagram.

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How to Find Full-Text Research Papers?

Once you have identified the papers you wish to read. You need to actually find the full-text research article. The majority should be available from the database you are using.

Sometimes you need to access the database first via your institution’s library website. This creates a proxy and the database will give you wider access to any paid journals your institution has signed up for.

If this does not work then try searching the specific article you want either in your library website or Google Scholar. Alternatively, you may need to go to the physical library and see if they have a printed copy.

Databases

• Medline – PubMed
• Web of Science
• Google Scholar
• Your Institution’s Library Website

Stay Organised

Manage Your Files

• Keep PDFs in a dedicated folder with useful titles
• Make notes on each research article
• Organise drafts of your writing by date
• Back-up your work on a separate USB or Cloud storage
• You can also try a free online reference manager for deciding whether to include or exclude papers with your team – https://www.rayyan.ai/

Use a Citation Manager

• Endnote
• Mendeley
• Others

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How to Extract Information for a Literature Review?

Make Notes

Make notes as you read each paper. Write down interesting things and themes that keep appearing in each of the papers you read. Make sure to either write the notes in your own words or put the copied text in quotes. This will help you avoid plagiarism later on. Also, keep track of which paper each piece of information came from so you don’t reference the incorrect author later on.

How to Critically Appraise Research Papers?

A good literature review does not simply summarise all of the available literature on a given topic, but it should critically discuss the important issues, identify problems with previous research and highlight gaps in current knowledge.

Key Aspects of Critical Thinking

• Identify evidence to back up and challenge key points
• Detect flaws and mistakes in the author’s reasoning
• Be aware of bias, or inadequate evidence
• Tell the difference between fact and opinion
• Evaluate conflicting opinions/ results
• Suggest solutions
• Make your own opinion

Tools to Help with Critical Appraisal:

The CASP tools are designed to help researchers critically appraise research papers. By following the questions in the CASP tool for each paper you will have a clear sense of the quality of the available literature and be able to form a clear critical analysis in your literature review.

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How to Structure Your Literature Review?

Your Literature Review will consist of the following basic headings:

• Introduction
• Methods
• Results
• Discussion
• Conclusion

One of the best ways to see how you should structure your literature review future is to follow your institution’s or publication’s guidelines. You may need specific tables or figures so it is best to reference those sources to see exactly what you need to do.

Check out this paper on writing an effective literature review for more tips – Link

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References

1. Pautasso M. (2013). Ten simple rules for writing a literature review. PLoS computational biology, 9(7), e1003149. Link
2. DCU