Shedding Light on PRISMA

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Systematic reviews (as well as other comprehensive evidence-based practice syntheses such as meta-analyses, scoping reviews, and living reviews) have in recent years become a buzzword in scientific publishing. However, many clinicians and researchers are unaware of the amount of time and effort these reviews require, and are not prepared for the process ahead.

The MSK Library’s Systematic Review Service provides resources and support for teams conducting comprehensive evidence-based reviews. One of the most important aspects of any comprehensive review is understanding, at minimum, what needs to be included. Thankfully, there are multiple tools and guidelines to assist you, including PRISMA.

What is PRISMA?

PRISMA is an evidence-based minimum set of items for reporting in systematic reviews and meta-analyses, to assist authors in improving the quality of their reviews.

PRISMA stands for: Preferred Reporting Items for Systematic Reviews and Meta-Analyses

The guidelines were originally developed in 2009, and included a statement and an explanation published in a variety of biomedical journals (including JAMA, NEJM, Lancet, and BMJ). Beginning in 2017 an international team updated the PRISMA guidelines to continue to reflect the changing nature of scientific communication. PRISMA 2020 was initially released as a preprint in September 2020 and published in March 2021 in the Journal of Clinical Epidemiology, and reprinted in a number of other journals to disseminate it widely. The PRISMA 2020 Statement consists of a 27-item checklist and a flow diagram.

There are a few components to PRISMA that provide different information and are used for different things.

The PRISMA Checklist

The PRISMA 2020 statement includes a 27-item checklist that addresses the introduction, methods, results and discussion sections of a systematic review report. An expanded checklist is also available that provides detailed information and recommendations about how to properly report each item, as found in the Explanation and Elaboration paper.

The PRISMA Flow Diagram

The PRISMA 2020 flow diagram shows the flow of information through the different phases of a systematic review. It outlines the number of records identified, included and excluded, and the reasons for exclusions.

PRISMA 2020 includes four different flow diagram templates based on the type of review and the sources used to identify studies:

  • new systematic reviews, includes searches of only databases and registers
  • updated systematic reviews, includes searches of only databases and registers
  • new systematic reviews, includes searches of databases and registers, plus other sources
  • updated systematic reviews, includes searches of databases and registers, plus other sources

PRISMA Extensions

Since 2015, a variety of extensions of the PRISMA Statement have been developed to facilitate the reporting of different types or aspects of systematic reviews, including:

Using PRISMA: Do This, Not That

PRISMA is a reporting guideline, not a how-to guideline. It is only designed to assist you in how to write up (aka report) the review process.

If you are reporting a systematic review, scoping review, meta-analysis, etc using PRISMA, you can describe it in your methods section like this:

  • “this review is reported according to PRISMA”
  • “we followed the PRISMA Statement to report this review”

These are examples of descriptions should NOT be used when writing up your review:

  • “we conducted the search according to PRISMA”
  • “the review conducted in accordance with PRISMA”

PRISMA-S: Reporting Literature Searches

The latest installment of PRISMA extensions is the PRISMA-S, an extension published in 2021, which is a 16-item checklist used to complement the PRISMA 2020 checklist and flow diagram, that focuses specifically on what needs to be included when reporting the literature search strategies for your review. Again, this is now a how-to, and your methods section should not describe your literature searches as conducted using PRISMA-S. Rather, it details what information should be included when writing up or reporting your review.

Some of the details that PRISMA-S recommends including in your write-up (either in the methods section or supplemental appendices) are:

  • database name and platform (eg. MEDLINE database on the Ovid platform)
  • full search strategies for every database and register included
  • other sources or methods used to identify studies (hand searching, author contacts, grey literature, etc.)
  • any limits, filters, or restrictions used or put into the searches
  • dates of all searches and updates
  • process and software used to manage citations, including removing duplicates (EndNote, Covidence, Distiller SR, etc.)

The Future of PRISMA

The following PRISMA extensions are in development in collaboration with the PRISMA group: