LITERATURE SEARCHING FOR RANDOMIZED CONTROLLED TRIALS USED IN COCHRANE REVIEWS: RAPID VERSUS EXHAUSTIVE SEARCHES

Pamela Royle · Ruairidh Milne

693 citations0/0 files storedInternational Journal of Technology Assessment in Health Care

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Meta-analysis and systematic reviews scientometrics and bibliometrics research Pharmaceutical industry and healthcare

Abstract

OBJECTIVES: To analyze sources searched in Cochrane reviews, to determine the proportion of trials included in reviews that are indexed in major databases, and to compare the quality of these trials with those from other sources. METHODS: All new systematic reviews in the Cochrane Library, Issue1 2001, that were restricted to randomized controlled trials (RCTs) or quasi-RCTs were selected. The sources searched in the reviews were recorded, and the trials included were checked to see whether they were indexed in four major databases. Trials not indexed were checked to determine how they could be identified. The quality of trials found in major databases was compared with those found from other sources. RESULTS: The range in the number of databases searched per review ranged between one and twenty-seven. The proportion of the trials in the four databases were Cochrane Controlled Trials Register = 78.5%, MEDLINE = 68.8%, Embase = 65.0%, and Science/Social Sciences Citation Index = 60.7%. Searching another twenty-six databases after Cochrane Controlled Trials Register (CCTR), MEDLINE, and Embase only found 2.4% additional trials. There was no significant difference between trials found in the CCTR, MEDLINE, and Embase compared with other trials, with respect to adequate allocation concealment or sample size. CONCLUSIONS: There was a large variation between reviews in the exhaustiveness of the literature searches. CCTR was the single best source of RCTs. Additional database searching retrieved only a small percentage of extra trials. Contacting authors and manufacturers to find unpublished trials appeared to be a more effective method of obtaining the additional better quality trials.

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References

2001Assessing the quality of controlled clinical trials 2001Reported Methodologic Quality and Discrepancies between Large and Small Randomized Trials in Meta-Analyses 2000Publication and related bias in meta-analysis 2001Investigating and dealing with publication and other biases in meta-analysis 2002Direction and impact of language bias in meta-analyses of controlled trials: empirical study 2000Does the inclusion of grey literature influence estimates of intervention effectiveness reported in meta-analyses?

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