Author Affiliations: School of Medicine, University of Pennsylvania, Philadelphia (Dr Berlin), and JAMA, Chicago, Ill (Dr Rennie).
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criteria, even those unpublished, to produce an unbiased estimate of the intervention's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.
Berlin JA, Rennie D. Measuring the Quality of TrialsThe Quality of Quality Scales. JAMA. 1999;282(11):1083-1085. doi:10.1001/jama.282.11.1083