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Systematic Reviews: Home

By Paul Levett

PRISMA 2020 revised guideline

The PRISMA guideline was recently revised and updated, all systematic reviews should now follow the PRISMA 2020 guideline described in the journal article Page, M. J. et al. (2021). The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ, 372: n71.

The key documents on the PRISMA statement website have been updated to reflect the PRISMA 2020 updates, see

This guide was originally written to accord with PRISMA 2009 and will be updated continually as PRISMA 2020 documents become available.

Need Assistance with a Systematic Review?

Are you currently working on a systematic review or research project and need assistance with search strategies and literature reviews? Himmelfarb Reference Librarians are skilled researchers who are trained to assist you with your review.  A recent JAMA article extolled the benefits of using a medical librarian to improve the quality of a systematic review of the medical literature.

Let us:

  • Identify search terms & expert search strategies
  • Select key databases and grey literature resources
  • Assist in finding relevant articles
  • Upload the search results into Covidence
  • Help in writing the methodology section of the review

If you would like to find out more information regarding these services, please contact the Reference and Instruction department at or 202-994-2850.

Covidence: Systematic Review Management

Covidence is an online tool that streamlines parts of the systematic review process. It makes it easy to screen references (both title/abstract and full-text), create and populate data extraction forms, and complete your risk of bias tables. You can also divide up the work among your team of reviewers, and track the progress of the project.



If you are considering a systematic review project, you should first consider its purpose.  If you are investigating a well defined problem for which there exists several large clinical trials that follow quantitative research methods you will want to write an analytical review to summarise the results of trials, analyze and combine the effect estimates reported in several studies, to provide cumulative evidence about the efficacy of one specific intervention/treatment/dose.  If you are investigating a less well understood problem for which there are few trials and/or you are reviewing observational data/qualitative research you will want to write a narrative review or narrative synthesis.

Having decided what type of literature review you wish to carry out, the next decision to think about is what is best way to present the information to your audience.  

For a small audience such as journal club, grand rounds, or a conference proceedings, an analytical review can be summarised in a short review format such as: Cairns, J. (2012). ACP Journal Club. Review: Dabigatran increases MI and reduces mortality compared with warfarin, enoxaparin, or placebo. Annals Of Internal Medicine, 156(12), JC6-JC11. doi:10.7326/0003-4819-156-12-201206190-02011.

Alternatively you may wish to present the results of your literature review as a poster presentation such as: Abualenain, J., Alabdrabalnabi, T., Rasooly, I., Pines, J., Levett, P. (2013). The Impact of Interventions to Reduce Length of Stay in the Emergency Department: A Systematic Review. Poster presented by Dr. Abualenain at the Society for Academic Emergency Medicine (SAEM) 2013 Annual Meeting in Atlanta, Georgia, May 14-18, 2013.  

Or publish your literature review in a journal article such as: Wilder, M. E., Kulie, P., Jensen, C., Levett, P., Blanchard, J., Dominguez, L. W., Portela, M., Srivastava, A., Li, Y., & McCarthy, M. L. (2021). The Impact of Social Determinants of Health on Medication Adherence: a Systematic Review and Meta-analysis. Journal of general internal medicine, 10.1007/s11606-020-06447-0.

When writing up the results of your systematic review for publication in a journal article for a wider professional audience you will need to include more detail about the methods you followed and the decisions you made on what studies to include/exclude from your review of the medical literature.  For a narrative review guidelines on how to write up for publication are on the next tab of this research guide titled Types of literature review & methods. The rest of this research guide will focus on how to write up for publication an analytical review following the PRISMA guidelines (Preferred Reporting Items for Systematic Reviews and Meta-Analyses).

The PRISMA guidelines consist of a 27-item checklist of items to report in the manuscript, a 16-item checklist for reporting the literature search strategy, and a four phase flow diagram.  PRISMA is an evidence-based minimum set of items for reporting in systematic reviews and meta-analyses.

Current guidance as of 2021

The PRISMA guideline has recently been revised and updated, systematic reviews should now follow the guidance in the journal article Page, M. J. et al. (2021). The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ, 372: n71.

Previous guidance

The PRISMA 2009 guidelines were originally introduced in the journal article Liberati, A,, Altman, D,, Moher, D, et al. (2009). The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: explanation and elaboration. Plos Medicine, 6(7):e1000100. doi:10.1371/journal.pmed.1000100 

It's a good idea to look at some examples of other review articles that cite this paper to see how the authors reported their systematic review following the PRISMA checklist.  Here is a search in the PubMed database for example reviews that have followed either the PRISMA 2020 format or the PRISMA 2009 format.

The PRISMA Group have developed several extensions to the original PRISMA reporting standard for different types or aspects of systematic reviews, they include the following:

From the librarian perspective an important extension is

Rethlefsen, M.L., Kirtley, S., Waffenschmidt, S. et al. PRISMA-S: an extension to the PRISMA Statement for Reporting Literature Searches in Systematic Reviews. Syst Rev 10, 39 (2021).

that amends how to report the database search strategy, the original requirement was to report the search syntax used for just one of the databases, but this extension changes this to require reporting of the search syntax used for each and every database searched for the literature review.


The Librarian's Role in the Systematic Review

Here is a summary of what support Himmelfarb Librarians can offer to help with the literature search for your systematic review.

The Institute of Medicine's (2011) Standard (3.1.1) for Systematic Reviews suggests the review team "work with a librarian or other information specialist trained in performing systematic reviews to plan the search strategy."  This guide outlines the role of the librarian in concordance with certain items in the Methods and Results sections of the PRISMA checklist:


  • Item 5 Protocol and registration
  • Item 6 Eligibility criteria
  • Item 7 Information sources
  • Item 8 Literature Search
  • Item 9 Study selection criteria
  • Item 10 Data collection process
  • Item 12 Screening for quality/Controlling for the risk of bias in individual studies


  • Item 17 Number of studies screened and number selected
  • Item 18 Characteristics of included studies
  • Item 20 Results of individual studies & summary of the data reported

Systematic vs Literature review

Systematic review vs literature review

Source: Kysh, L. (2013). What's in a name? The difference between a systematic review and a literature review and why it matters. University of Southern California, Norris Medical Library.