When to update systematic reviews and how to do it: consensus and checklist

SUMMARY
Updating systematic reviews is, in general, more efficient than starting afresh when new evidence emerges. The Panel for Updating Guidance for Systematic reviews (PUGs), comprising review authors, editors, statisticians, information specialists, related methodologists, and guideline developers, met to develop guidance for people considering updating systematic reviews. The Panel proposed the following:
1. Decisions about whether and when to update a systematic review are judgements made for individual reviews at a point in time. This can be made by agencies responsible for systematic review portfolios, journal editors with systematic review update services, or author teams considering embarking on an update of a review.
2. The decision needs to take into account whether the review addresses a current question, uses valid methods and is well conducted; whether there are new relevant methods, new studies, or new information on existing included studies. Given this information, the agency, editors or authors need to judge whether the update will influence the review findings or credibility sufficiently to justify the effort in updating it.
3. The Panel proposed a decision framework to navigate and report these decisions, and noted that incorporating new synthesis methods such as GRADE is often likely, in addition, to improve the quality of the analysis and the clarity of the findings.
4. Given a decision to update, the process needs to start with an appraisal and revision of the background, question, inclusion criteria, and methods of the existing review.
5. Search strategies should be refined, taking into account changes in the question or inclusion criteria. An analysis of yield from the previous edition, in relation to databases searched, terms, and languages can make searches more specific and efficient.
6. In many instances an ‘Update’ represents a new edition of the review, and authorship of the new version needs to follow ICMJE criteria; new approaches to publishing licences could help new authors build on and re-use the previous edition while giving appropriate credit to the previous authors.
The Panel also considered this guidance in the context of emerging technological advances in software, information retrieval, and electronic linkage and mining. With good synthesis and technology partnerships, these advances could revolutionise the efficiency of updating in the coming years.