Identifying additional studies for a systematic review of retention strategies in randomised controlled trials: making contact with trials units and trial methodologists
- PMID: 28830570
- PMCID: PMC5568351
- DOI: 10.1186/s13643-017-0549-9
Identifying additional studies for a systematic review of retention strategies in randomised controlled trials: making contact with trials units and trial methodologists
Abstract
Background: Search strategies for systematic reviews aim to identify all evidence relevant to the research question posed. Reports of methodological research can be difficult to find leading to biased results in systematic reviews of research methodology. Evidence suggests that contact with investigators can help to identify unpublished research. To identify additional eligible randomised controlled trials (RCTs) for a Cochrane systematic review of strategies to improve retention in RCTs, we conducted a survey of UK clinical trials units (CTUs) and made contact with RCT methodologists.
Methods: Key contacts for all UK CTUs were sent a personalised email with a short questionnaire and summary protocol of the Cochrane methodology review. The questionnaire asked whether a RCT evaluating strategies to improve retention embedded in a RCT had ever been conducted by the CTU. Questions about the stage of completion and publication of such RCTs were included. The summary protocol outlined the aims, eligibility criteria, examples of types of retention strategies, and the primary outcome for the systematic review. Personal communication with RCT methodologists and presentations of preliminary results of the review at conferences were also used to identify additional eligible RCTs. We checked the results of our standard searches to see if eligible studies identified through these additional methods were also found using our standard searches.
Results: We identified 14 of the 38 RCTs included in the Cochrane methodology review by contacting trials units and methodologists. Eleven of the 14 RCTs identified by these methods were either published in grey literature, in press or unpublished. Three remaining RCTs were fully published at the time. Six of the RCTs identified were not found through any other searches. The RCTs identified represented data for 6 of 14 RCTs of incentive strategies (52% of randomised participants included in the review), and 6 of 14 RCTs of communication strategies (52% of randomised participants included in the Cochrane review). Data were unavailable for two of the RCTs identified.
Conclusions: Methodological evaluations embedded in RCTs may be unpublished, published in the grey literature or where published, poorly indexed in bibliographic databases. To identify such studies and minimise selection bias in systematic reviews of methodological evaluations, reviewers should consider contacting CTUs and trial methodologists.
Keywords: Methodology review; Personal communication; Searching for methodological research; Survey; Systematic review methods; Unpublished data.
Conflict of interest statement
Ethics approval and consent to participate
The survey of UK CTUs focused on identifying additional eligible studies to include in a Cochrane systematic review and was conducted in full knowledge of the senior management at the MRC CTU. Consent to participate in the survey was considered given when the CTU key contact replied to the initial email. The Cochrane review contributed to a PhD thesis. Ethics approval for a qualitative study associated with the PhD thesis was sought from the University College London Ethics Committee UCL 2342/002.
Consent for publication
No individual person’s data was used for this research.
Competing interests
The authors declare that they have no competing interests.
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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