Searching and reporting in Campbell Collaboration systematic reviews: A systematic assessment of current methods

The search methods used in systematic reviews provide the foundation for establishing the body of literature from which conclusions are drawn and recommendations made. Searches should aim to be comprehensive and reporting of search methods should be transparent and reproducible. Campbell Collaboration systematic reviews strive to adhere to the best methodological guidance available for this type of searching. The current work aims to provide an assessment of the conduct and reporting of searches in Campbell Collaboration systematic reviews. Our objectives were to examine how searches are currently conducted in Campbell systematic reviews, how search strategies, search methods and search reporting adhere to the Methodological Expectations of Campbell Collaboration Intervention Reviews (MECCIR) and PRISMA standards, and identify emerging or novel methods used in searching in Campbell systematic reviews. We also investigated the role of information specialists in Campbell systematic reviews. We handsearched the Campbell Systematic Reviews journal tables of contents from January 2017 to March 2024. We included all systematic reviews published since 2017. We excluded other types of evidence synthesis (e.g., evidence and gap maps), updates to systematic reviews when search methods were not changed from the original pre-2017 review, and systematic reviews that did not conduct their own original searches. We developed a data extraction form in part based on the conduct and reporting items in MECCIR and PRISMA. In addition, we extracted information about the general quality of searches based on the use of Boolean operators, keywords, database syntax and subject headings. Data extraction included information about reporting of sources searched, some aspects of search quality, the use and reporting of supplementary search methods, reporting of the search strategy, the involvement of information specialists, date of the most recent search, and citation of the Campbell search methods guidance. Items were rated as fully, partially or not conducted or reported. We cross-walked our data extraction items to the 2019 MECCIR standards and 2020 PRISMA guidelines and provide descriptive analyses of the conduct and reporting of searches in Campbell systematic reviews, indicating level of adherence to standards where applicable. We included 111 Campbell systematic reviews across all coordinating groups published since 2017 up to the search date. Almost all (98%) included reviews searched at least two relevant databases and all reported the databases searched. All reviews searched grey literature and most (82%) provided a full list of grey literature sources. Detailed information about databases such as platform and date range coverage was lacking in 16% and 77% of the reviews, respectively. In terms of search strategies, most used Boolean operators, search syntax and phrase searching correctly, but subject headings in databases with controlled vocabulary were used in only about half of the reviews. Most reviews reported at least one full database search strategy (90%), with 63% providing full search strategies for all databases. Most reviews conducted some supplementary searching, most commonly searching the references of included studies, whereas handsearching of journals and forward citation searching were less commonly reported (51% and 62%, respectively). Twenty-nine percent of reviews involved an information specialist co-author and about 45% did not mention the involvement of any information specialist. When information specialists were co-authors, there was a concomitant increase in adherence to many reporting and conduct standards and guidelines, including reporting website URLs, reporting methods for forward citation searching, using database syntax correctly and using subject headings. No longitudinal trends in adherence to conducting and reporting standards were found and the Campbell search methods guidance published in 2017 was cited in only twelve reviews. We also found a median time lag of 20 months between the most recent search and the publication date. In general, the included Campbell systematic reviews searched a wide range of bibliographic databases and grey literature, and conducted at least some supplementary searching such as searching references of included studies or contacting experts. Reporting of mandatory standards was variable with some frequently unreported (e.g., website URLs and database date ranges) and others well reported in most reviews. For example, database search strategies were reported in detail in most reviews. For grey literature, source names were well reported but search strategies were less so. The findings will be used to identify opportunities for advancing current practices in Campbell reviews through updated guidance, peer review processes and author training and support.