Introduction. This paper provides an overview of the information retrieval strategy employed for two meta-analyses, conducted by a systematic review team at Concordia University (Montreal, QC, Canada). Both papers draw on standards first articulated by H.M. Cooper and further developed by the Campbell Collaboration, which promote a comprehensive approach to systematically searching an extensive array of resources (bibliographic databases, print resources, citation indices, etc.) in order to locate both published and unpublished research. The goal is to verify if searching comprehensively through multiple resources retrieves studies that are unique, and hence, improve the overall representativeness of a diverse body of literature. We also analyze the sensitivity and specificity of the results by data source.

Methods. In order to determine the source sensitivity, we consider percentage of results from each source retrieved for full-text review. In order to determine the source specificity, we derive a percentage from the total number of studies included in the final meta-analysis compared against the overall number of initial results found.

Results. Results demonstrate the need to search beyond the subject-specific databases of a particular discipline as unique results can be found in many places. Databases for related disciplines provided 129 unique includes to each meta-analysis, and multidisciplinary databases provided 44 and 99 unique includes for the two meta-analyses in question respectively. Manual search techniques were much more sensitive and specific than electronic searches of databases and yield a higher percentage of final includes.

Discussion. The results demonstrate the utility of a comprehensive information retrieval methodology like that proposed by the Campbell Collaboration, which goes beyond the main subject databases to locate the full range of information sources, including grey literature.