Using the Cochrane Central Register of Controlled Trials to identify clinical trial registration is insufficient: a cross-sectional study

Masahiro Banno,Yuki Kataoka,Yasushi Tsujimoto

doi:10.1186/s12874-020-01083-y

Abstract

BackgroundWhile conducting systemic reviews, searching for ongoing or unpublished trials is critical to address publication bias. As of April 2019, records of ongoing or unpublished randomized and/or quasi-randomized controlled trials registered in the International Clinical Trials Registry Platform (ICTRP) and ClinicalTrials.gov are available in the Cochrane Central Register of Controlled Trials (CENTRAL). These records registered in CENTRAL include studies published since the inception of ICTRP and ClinicalTrials.gov. Whether systematic reviewers can search CENTRAL to identify ongoing or unpublished trials instead of ICTRP and ClinicalTrials.gov is unknown.MethodsThis was a cross-sectional study. A consecutive sample of ongoing or unpublished studies published from June 1, 2019 to December 27, 2019 was selected from the Cochrane Reviews.The sensitivity and the number needed to read (NNR) were assessed from among the studies selected from CENTRAL instead of ICTRP and ClinicalTrials.gov and also assessed the characteristics of studies not identified by searching CENTRAL.ResultsIn total, 247 records from 50 Cochrane reviews were included; of these, 200 were identified by searching CENTRAL, whereas the remaining 47 records were not. The sensitivity of searching CENTRAL was 0.81 (95% confidence interval [CI]: 0.76, 0.85). The NNR was 115 (95% CI: 101, 133). The 47 unidentified studies were registered through ClinicalTrials.gov or ICTRP. Sixteen unidentified studies were not indexed in CENTRAL.ConclusionsFor systematic reviewers, searching CENTRAL could not substitute for searching ClinicalTrials.gov and/or ICTRP. Systematic reviewers should not only search CENTRAL but also ICTRP and ClinicalTrials.gov to identify unpublished trials.Trial registrationA pre-specified protocol was applied to conduct this study. The study was registered in the University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR). Trial registration number: UMIN000038981.

Highlights

While conducting systemic reviews, searching for ongoing or unpublished trials is critical to address publication bias
As of April 2019, records of ongoing or unpublished randomized controlled trials (RCTs) and quasi-randomized controlled trials since the inception of International Clinical Trials Registry Platform (ICTRP) and ClinicalTrials.gov have been included in the Cochrane Central Register of Controlled Trials (CENTRAL) [5], and newly submitted records are indexed in CENTRAL on a monthly basis [6]
Results in relation to prior studies These results demonstrating that searching CENTRAL alone is insufficient for identifying ongoing or unpublished clinical trials are similar to those of previous studies that have shown that searching the ICTRP, which included ClinicalTrials.gov, does not always retrieve all ClinicalTrials.gov records [1, 3, 4]

Summary

Introduction

As of April 2019, records of ongoing or unpublished randomized and/or quasi-randomized controlled trials registered in the International Clinical Trials Registry Platform (ICTRP) and ClinicalTrials.gov are available in the Cochrane Central Register of Controlled Trials (CENTRAL). These records registered in CENTRAL include studies published since the inception of ICTRP and ClinicalTrials.gov. As of April 2019, records of ongoing or unpublished randomized controlled trials (RCTs) and quasi-randomized controlled trials (quasi-RCTs) since the inception of ICTRP and ClinicalTrials.gov have been included in the Cochrane Central Register of Controlled Trials (CENTRAL) [5], and newly submitted records are indexed in CENTRAL on a monthly basis [6]. The aim of this study was to answer the question 1.“Can systematic reviewers rely on searching CENTRAL alone to identify ongoing and unpublished studies rather than conducting parallel searches of trial registries?” and 2.Examining the sensitivity and the number needed read (NNR) using CENTRAL to identify ongoing or unpublished studies

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Conclusion