Meta-Analyses of Randomized Controlled Trials

A new type of research, termed meta-analysis, attempts to analyze and combine the results of previous reports. We found 86 meta-analyses of reports of randomized controlled trials in the English-language literature. We evaluated the quality of these meta-analyses, using a scoring method that considered 23 items in six major areas — study design, combinability, control of bias, statistical analysis, sensitivity analysis, and application of results. Only 24 meta-analyses (28 percent) addressed all six areas, 31 (36 percent) addressed five, 25 (29 percent) addressed four, 5 (6 percent) addressed three, and 1 (1 percent) addressed two. Of the 23 individual items, between 1 and 14 were addressed satisfactorily (mean ±SD, 7.7±2.7). We conclude that an urgent need exists for improved methods in literature searching, quality evaluation of trials, and synthesizing of the results. (N Engl J Med 1987; 316:450–5.), RECENTLY, a number of papers have appeared in the medical literature that attempt to evaluate and combine the results of previous studies. Light and Smith¹ were among the first to propose pooling original data from various research studies. Glass was the first to refer to this type of research as “meta-analysis.”² A dictionary defines “meta” as “more comprehensive: transcending… — used with the name of a discipline to designate a new but related discipline designed to deal critically with the original one.”³ Thus, meta-analysis is a new discipline that critically reviews and statistically combines the results of…