%0 Journal Article
%T Investing in updating: how do conclusions change when Cochrane systematic reviews are updated?
%A Simon D French
%A Steve McDonald
%A Joanne E McKenzie
%A Sally E Green
%J BMC Medical Research Methodology
%D 2005
%I BioMed Central
%R 10.1186/1471-2288-5-33
%X This descriptive study examined all completed systematic reviews in the Cochrane Database of Systematic Reviews (CDSR) Issue 2, 1998. The latest version of each of these reviews was then identified in CDSR Issue 2, 2002 and changes in the review were described. For reviews that were updated within this time period and had additional studies, we determined whether their conclusion had changed and if there were factors that were predictive of this change.A total of 377 complete reviews were published in CDSR Issue 2, 1998. In Issue 2, 2002, 14 of these reviews were withdrawn and one was split, leaving 362 reviews to examine for the purpose of this study. Of these reviews, 254 (70%) were updated. Of these updated reviews, 23 (9%) had a change in conclusion. Both an increase in precision and a change in statistical significance of the primary outcome were predictive of a change in conclusion of the review.The concerns around a lack of updating for some reviews may not be justified considering the small proportion of updated reviews that resulted in a changed conclusion. A priority-setting approach to the updating of Cochrane systematic reviews may be more appropriate than a time-based approach. Updating all reviews as frequently as every two years may not be necessary, however some reviews may need to be updated more often than every two years.When people make decisions about health care they should have access to the most up-to-date and reliable evidence. Cochrane systematic reviews aim to provide healthcare professionals, consumers and policy makers with the 'best available' and most up-to-date evidence on the effects of healthcare interventions. One of the advantages of an electronic publication such as The Cochrane Library is that reviews are replaced with an updated version as this new evidence becomes available or mistakes are identified [1]. This differs from print journals where readers do not necessarily know if they are accessing the most up-to-date systematic
%U http://www.biomedcentral.com/1471-2288/5/33