Background: Overviews of systematic reviews attempt to systematically retrieve and summarise the results of multiple systematic reviews into a single document. Methods for conducting, interpreting and reporting overviews of reviews are in their infancy. To date, there has been no systematic review or evidence map examining the range of methods for overviews nor of the evidence for using these methods. The objectives of the study are to develop and populate a framework of methods that have or may be used in conducting, interpreting and reporting overviews of systematic reviews of interventions (stage I); create an evidence map of studies that have evaluated these methods (stage II); and identify and describe unique methodological challenges of overviews.
Methods: The research will be undertaken in two stages. For both stages, we plan to search methods collections (e.g. Cochrane Methodology Register, Meth4ReSyn library, AHRQ Effective Health Care Program) to identify eligible studies. These searches will be supplemented by searching reference lists and citation searching. Stage I: Methods used in overviews will be identified from articles describing methods for overviews, methods studies examining a cross section/cohort of overviews, guidance documents and commentaries. The identified methods will populate a framework of available methods for conducting an overview. Two reviewers will independently code included studies to develop the framework. Thematic analysis of the coded data will be used to categorise and describe methods. Stage II: Evaluations of the performance of methods will be identified from systematic reviews of methods studies and methods studies. Evaluations will be described and mapped to the framework of methods identified in stage I.
Discussion: The results of this process will be useful for mapping of methods for overviews of systematic reviews, informing guidance and identifying and prioritising method research in this field.