Systematic reviews and meta-analyses on treatment of asthma: critical evaluation

Objective To evaluate the clinical, methodological, and reporting aspects o f systematic reviews and meta-analyses on the treatment of asthma and to co mpare those published by the Cochrane Collaboration with those published in paper based journals. Design. Analysis of studies identified from Medline, CINAHL. HealthSTAR, EM BASE, Cochrane Library, personal collections, and reference lists. Studies Articles describing a systematic review or a meta-analysis of the t reatment of asthma that were published as a full report, in any language or format, in a peer reviewed journal or the Cochrane Library. Main outcome measures General characteristics of studies reviewed and metho dological characteristics (sources of articles; language restrictions; form at, design and publication status of studies included; type of data synthes is; and methodological quality). Results 50 systematic reviews and meta-analyses were included. More than ha lf were published in the past two years. Twelve reviews were published in t he Cochrane Library and 38 were published in 2 peer reviewed journals. Forc ed expiratory volume in one second was the most frequently used outcome, bu t few reviews evaluated the effect of treatment on costs or patient prefere nces. Forty reviews were judged to have serious or extensive nd rvs. All si x reviews associated with industry were in this group. Seven of the 10 most rigorous reviews were published in the Cochrane Library. Conclusions Most reviews published in peer reviewed journals or funded by i ndustry have serious methodological flaws that limit their value to guide d ecisions. Cochrane reviews are more rigorous and better reported than those published in peer reviewed journals.