How useful are unpublished data from the Food and Drug Administration in meta-analysis?

The goals of this systematic review and meta-analysis were to ascertain whether studies of nonsteroidal anti-inflammatory drugs (NSAIDs) summarized in the FDA reviews are ultimately published, to compare the methodologic and population characteristics of studies summarized in the FDA reviews with those reported in peer reviewed literature, and to compare the pooled relative risk of dyspepsia from NSAIDs in each data source. Summary measures of risk difference were calculated with a random effects model; meta-regression was used to assess the effect of study covariates. Among 37 studies described in the FDA reviews, one was published. Sample size, gender distribution, indication for drug use, and methodologic quality did not vary significantly between the published and FDA data. The pooled risk ratio for dyspepsia obtained using published data (1.21) or FDA data (1.07) did not differ significantly or practically. Data from FDA reviews may be a viable data source for systematic reviews and meta-analyses but only after being subjected to the same methodologic scrutiny as published data.