A multicomponent decision tool for prioritising the updating of systematic reviews.

Evidence evolves as new research becomes available, and thus systematic reviews should be kept up to date to maintain their relevance and validity. However, the decision to update a systematic review should be made carefully because updating is potentially resource intensive, and updating too soon could introduce bias. In contrast, if reviews are not updated frequently enough, doctors and policy makers could act on evidence that is out of date. There is currently no consensus on when to initiate updating. Traditionally, the Cochrane Collaboration used a biennial updating policy, yet many Cochrane reviews are out of date (fig 1⇓); only about 20% of reviews are updated every two years. As of February 2013, the Cochrane Database of Systematic Reviews, published in the Cochrane Library, contained 5418 reviews. This number implies that 2700 Cochrane reviews will need to be updated per year to comply with the updating policy, in addition to producing new reviews. Despite the emphasis on Cochrane reviews in this paper, updating is a common challenge, and methods are needed to prioritise reviews that are most in need of updating. A methodological review of different methods for identifying when to update a systematic review found that existing methods were not comprehensive because they only considered either qualitative or quantitative techniques. We describe a multicomponent (that is, including both qualitative and quantitative components) updating decision tool that can be used to determine when to prioritise one or more systematic reviews for updating. We provide a brief overview of the initial development and evaluation of the two complementary components, describe how they have been improved and integrated to produce the decision tool, and give illustrative examples of its implementation. Development and evaluation of the qualitative decision tree