Chapter 3 – Identifying Randomized Controlled Trials – Systematic Reviews in Health Research

Julie Glanville, Carol Lefebvre

Abstract

In 1993, before the establishment of Cochrane (formerly the Cochrane Collaboration), only 19 000 reports of randomized controlled trials were readily identifiable (i.e. indexed as such) in MEDLINE, though there were many more within the database. In 1996, the Cochrane Central Register of Controlled Trials (CENTRAL) was launched, in the Cochrane Library, and now contains nearly 2 million records or reports of trials from MEDLINE, Embase, ClinicalTrials.gov, and other sources. In addition to CENTRAL, other sources should be searched to try to minimize publication bias, such as national, international, and regional databases; subject-specific databases; trials registers, regulatory agency sources, and sources of clinical study reports; and sources specific to systematic reviews. A number of recent initiatives have contributed to greater transparency in trial registration and reporting, but much remains to be done. Highly sensitive, but adequately precise, searches of appropriate sources are fundamental to the process of conducting reliable, trustworthy systematic reviews.

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Author affiliations

Julie Glanville

Glanville.info, York

Carol Lefebvre

Lefebvre Associates Ltd, Oxford, UK

How to cite this chapter?

For the printed version of the book

Glanville, J. and Lefebvre, C. (2022). Chapter 3. Identifying randomized controlled trials. In: Systematic Reviews in Health Research: Meta-analysis in Context (eds M. Egger, J.P.T. Higgins and G. Davey Smith), pp 36-54. Hoboken, NJ : Wiley.