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September 15, 1999

Measuring the Quality of TrialsThe Quality of Quality Scales

Author Affiliations

Author Affiliations: School of Medicine, University of Pennsylvania, Philadelphia (Dr Berlin), and JAMA, Chicago, Ill (Dr Rennie).

JAMA. 1999;282(11):1083-1085. doi:10.1001/jama.282.11.1083

Physicians seeking the best information about particular interventions often turn to the results of meta-analyses. Meta-analyses, if done correctly according to explicit rules, will include all relevant studies that meet specified criteria, even those unpublished, to produce an unbiased estimate of the intervention's worth. If the quality of the component studies of a meta-analysis is poor, then a precise summary of those poor studies is unjustified. Since poor-quality studies sometimes produce systematically different results, for example, larger treatment effects,1,2 a meta-analysis may not only be deceptively precise, but may yield misleading results. In an attempt to deal directly with issues of study quality, many meta-analyses of therapeutic issues restrict consideration to randomized controlled trials.

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