Our review updating process
Much has been published on issues around the methodology of systematic reviews, including the QUOROM statement.[2] Yet there is no consensus and little research about how frequently systematic reviews should be updated.[3]
Annual updating
In the past, we aimed to update every Clinical Evidence review annually. However our experience has shown that not all our reviews benefit from an annual update, in particular those where there is little high quality, important new evidence published on a regular basis. This belief is supported by studies which have found changes to the conclusions in less than 10% of updated reviews[4], and that only 23% of systematic reviews actually merit an update within two years, as determined by substantial changes to data on effectiveness or harms of treatments.[5] Importantly, there may be harm from too frequent updating of reviews where new research is sparse, as there may be a temptation to change a conclusion based on a limited number of small studies, only to change it back when the more complete research picture becomes clear with the publication of more and larger trials.
Move to continuous updating
We have reviewed this strategy recently in accordance with a more sophisticated approach to our handling of information, and in line with other large producers of systematic reviews, such as the Cochrane Library. We have therefore developed a new updating strategy for Clinical Evidence reviews, based on the content of the review, the number of new RCTs and systematic reviews being published on the topic each year, and the popularity of the review with users of our website.
Tailored updating schedules
By moving to this new system each review will have a tailored updating schedule which relates to the review itself, rather than a non-specific general policy. These tailored review updating plans will allow us to produce better quality systematic reviews and make best use of our authors' and reviewers' time.
The updating schedule is supported by a continuous review of the evidence by Evidence Updates.
Your views
We are excited about these developments, and welcome your feedback on this new approach. Please contact Dr Charles Young, Editor of Clinical Evidence, (Charles.Young@bmjgroup.com) if you would like to discuss further.
References
- Enkin M, Keirse M, Renfrew M, et al. A guide to effective care in pregnancy and childbirth. Oxford: Oxford University Press, 1998.
- Moher D, Cook DJ, Eastwood S et al. Improving the quality of reports of meta-analyses of randomised controlled trials: the QUOROM statement. Lancet 1999;354:1896-1900.
- Moher D, Tsertsvadze A, Tricco A, Eccles M, Grimshaw J, Sampson M, Barrowman N. When and how to update systematic reviews. Cochrane Database of Systematic Reviews 2008, Issue 1. Art. No.: MR000023. DOI:10.1002/14651858.MR000023.pub3.
- French SD, McDonald S, McKenzie JE et al. Investing in updating: how do conclusions change when Cochrane systematic reviews are updated? BMC Med Res Methodol 2005;5:33.
- Shojania KG, Sampson M, Ansari MT et al. How quickly do systematic reviews go out of date? A survival analysis. Ann Intern Med 2007;147:224-233.