PRISMA 2009 Versus 2020

The Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) is one of the most popular tools for systematic reviews. In the 1980s, Cynthia Mulrow discovered major deficiencies in the quality of review reports. Decades of work led to PRISMA being published in 2009.

PRISMA proposed a guideline to help systematic reviewers transparently report information about a systematic review, including why the review was done, what the authors did, and what they found. PRISMA provides readers with the information needed to form their own views about how well a review was carried out and how applicable the findings are to their own settings.

In 2020, PRISMA published a new reporting guidance that reflects advances in methods to identify, select, appraise, and synthesize studies. What are the PRISMA statement guidelines, and how were they updated?

The PRISMA Statement

The PRISMA statement guidelines consist of a checklist and a flow diagram. The checklist details the 27 items that must be reported in every review; these items are checked off the list as they are completed. The PRISMA guideline gives the rationale for each checklist item, along with useful examples, and the PRISMA flow diagram reports the decisions that the review team took as they assessed citations for possible inclusion in the review.

PRISMA 2009 Versus PRISMA 2020

PRISMA 2020 was published after more than a decade of advances in systematic review methods since the initial version. Like PRISMA 2009, PRISMA 2020 has a checklist of 27 items, but some of the wording has been revised and updated. The update uses more inclusive wording, and is more accommodating to other methods from different fields. In addition, some items in the checklist now contain sub-items – a detail absent in PRISMA 2009. This gives reviewers more clarity about what exactly they should be reporting.

There is an obvious push for transparency with PRISMA 2020. Reviewers are now required to include the full search strategies and the number of results obtained for all searches. Additionally, they must include complete citations for all studies included, as well as citations for any studies that were disregarded at the full-text stage, along with justification.

The selection process for the PRISMA 2020 systematic review now includes reporting on how many reviewers screened each record and each report, whether they worked independently, and if any automation was used.

Technological advances in the last decade have also enabled the use of natural language processing and machine learning in reviews. Machine learning can now be used to identify relevant evidence, and new methods have been developed to assess the risk of bias in the results of included studies. PRISMA 2020 adds the ability to report the use of these tools.

The updated PRISMA 2020 flow diagram is more flexible than PRISMA 2009, adding optional fields that allow reporting of review updates. On the PRISMA website, reviewers also now have four variations of the flow diagram template to choose from.