Undertaking systematic reviews of research on effectiveness: CRD's guidance for carrying out or commissioning reviews

In this document, the framework for carrying out systematic reviews is described in three stages: planning, reviewing and disseminating. The need for a review should be established before commissioning or commencing review work. The methodology of the review should be documented and working arrangements should be put in place to ensure that the methods can be followed. Finally, there should be a strategy for putting together a report of the review and disseminating its findings to relevant audiences, and if possible, updating the review.

The stages of a review and the phases within them are described consecutively. However, this chronology may vary during the review. It will not always be possible to complete one phase before another has to be started, and sometimes it will be more efficient to work on several phases simultaneously.

It is essential that good communication is maintained between those commissioning or supervising the review and those carrying it out. To aid the process, this framework includes agendas for some joint meetings. These meetings help set a timetable and ensure that the review work receives the required direction and support. The number of meetings and their schedule may have to be tailored to suit the requirements of a given review.

The content of this report draws on information from several sources. All the steps necessary to undertake a systematic review have been listed, but it is not possible to provide definitive advice on all of the methods. This is because the science of systematically reviewing the literature is relatively young, and many methodological issues are still being explored. Therefore this guidance is to assist those conducting reviews to reach a minimum standard based on the understanding of the subject at the time of writing. Reviewers wishing to obtain up-to-date information in this area should look at the Cochrane Methodology Database and systematic reviews of empirical methodological research in the Cochrane Library. New advice is incorporated in updates of the Cochrane Reviewers' Handbook (URL: http://www.updatesoftware. com/ccweb/cochrane/hbook.htm) and the ‘Resources available at the CRD’ web site (URL: http:// www.york.ac.uk/inst/crd/).