Background: Exponential increase in the number of systematic reviews published, and constrained resources for new reviews, means that there is an urgent need for guidance on explicitly and transparently integrating existing reviews into systematic reviews. The objectives of this paper are: (1) to identify areas where existing guidance may be adopted or adapted, and (2) to suggest areas for future guidance development.
Methods: We searched documents and Web sites from systematic review organizations to identify and, where available, summarize relevant guidance on the use of existing systematic reviews. We conducted informational interviews with members of Evidence-based Practice Centers (EPCs) to gather experiences in integrating existing systematic reviews, including common issues and challenges, as well as potential solutions.
Results: There was consensus among systematic review organizations and the EPCs about some aspects of incorporating existing systematic reviews. However, areas of challenge remain. Areas in need of guidance include how to synthesize, grade the strength of, and present bodies of evidence composed of primary studies and existing systematic reviews.
Conclusions: There remain areas of uncertainty for how to integrate existing systematic reviews. Methods research along with future EPC program methods workgroups are needed to address these challenges.