Clinical trial registry searching: do Cochrane protocol search methods match good practice?




Poster session 5


Thursday 27 October 2016 - 10:30 to 11:00


All authors in correct order:

Berber S1, Tan-Koay AG1, Askie LM2, Lasserson TJ3, Willson ML1
1 Cochrane Breast Cancer Group, NHMRC Clinical Trials Centre, Australia
2 ANZCTR and Systematic Reviews and Health Technology Assessments, NHMRC Clinical Trials Centre, Australia
3 Cochrane Editorial Unit, Cochrane Central Executive, UK
Presenting author and contact person

Presenting author:

Slavica Berber

Contact person:

Abstract text
Background: In systematic reviews, searching trial registries is important in detecting the risk of publication bias and indicating the breadth of ongoing trials. The Cochrane conduct and reporting standards recommend searching both ( and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) and reporting of search terms used (1,2). Compliance with these recommendations within Cochrane reviews is unknown.

Objectives: To describe the current practices in searching trial registries in published Cochrane protocols.

Methods: We conducted a preliminary audit of Cochrane protocols published in Issues 1 to 3 (2016) in the Cochrane Library. We extracted information on whether or not 1) the Methods section described searching and ICTRP, 2) the Methods or Appendices reported the search terms used in or ICTRP, and 3) the Methods or Appendices reported the search strings on either the basic or advanced search functions or both. Findings were reported as frequencies and percentages.

Results: From 142 protocols identified, 44 were excluded due to being marked as withdrawn (36) or relating to either an overview (3) or a diagnostic test accuracy review (5). Of the 98 audited protocols, 88 (90%) mentioned searching both and ICTRP in the methods section while six protocols intended to search either or ICTRP. Of these 88 protocols, 30 protocols provided either search terms only (4) or search strings (26). The search strings provided in the protocols were in the form of: basic search only (8/26), advanced search only (12/26), basic or advanced search for each registry (4/26), or both basic and advanced searches (2/26).

Conclusions: The majority of audited protocols described both and ICTRP as part of their searching resources but did not frequently provide search terms/strings. As ongoing trial research assists us in assessing the overall completeness of the evidence, further improvements in detailing search strings for trial registries is needed.