Hunter 2022

 Reviewer(s): 

Alan Lovell,  

Juliet Brown, 

MS Copilot 

Full Reference: 

Hunter, K. E., Webster, A. C., Page, M. J., Willson, M., McDonald, S., Berber, S., Skeers, P., TanKoay, A. G., Parkhill, A., & Seidler, A. L. (2022). Searching clinical trials registers: guide for systematic reviewers. BMJ, 377, e068791. https://doi.org/10.1136/bmj-2021-068791

Short Description: 

This Methods and Reporting paper provides comprehensive, stepbystep guidance for systematically searching clinical trials registers to identify unpublished and ongoing studies for inclusion in systematic reviews. Drawing on literature review, expert consensus, surveys of information specialists, and a worked case study (TOPCHILD), the authors outline 11 structured steps covering where to search, how to design and execute search strategies, record management, screening, data extraction, updating searches, and transparent reporting. 

The guidance emphasizes searching both ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform, cautions against overly restrictive filters, and highlights the value of trial registers for detecting publication bias and accessing unpublished results. The TOPCHILD case study demonstrates the practical impact: 15 out of 71 eligible trials were identified only through register searches. The authors argue that rigorous register searching reduces bias, research waste, and strengthens the validity of systematic reviews

. Limitations Stated by the Author(s): 

• Trial register search interfaces are often unsophisticated, unstable, and inconsistent, which can reduce sensitivity and efficiency. 

• Registry data can be incomplete, inaccurate, or outdated (e.g. recruitment status). 

• Obtaining unpublished results or individual participant data frequently requires direct investigator contact and may not always be successful. 

• Guidance is resourceintensive and may be challenging for reviewers with limited time, expertise, or institutional support

Limitations Stated by the Reviewer(s): 

• The guidance is largely based on expert consensus, surveys, and case study illustration rather than formal empirical evaluation of effectiveness. 

• Findings from the TOPCHILD case study may not generalise to all clinical areas or nontrial research questions. 

• Implementation may be difficult in rapid reviews or lowresource settings due to the time and technical demands of registry searching. 

• The paper does not quantify the relative gain from register searching across different topic areas.