Meta-analysis and meta-analytic monitoring of clinical trials.

Randomized trials are effective and usually unbiased for showing the average results in a selected outcome variable for treatment A versus treatment B, and meta-analyses produce an average of these averages. The results of both the trials and meta-analyses are often pragmatically unsatisfactory, however, because they do not reflect cogent distinctions desired by practising clinicians in the heterogeneous subgroups formed by diverse components in the patients' baseline states, in proficiency of therapy, and in additional outcome phenomena. If the inadequacies of previous trials have led to performance of a suitable new trial, it should not be stopped by the numbers emerging from meta-analyses of prior non-pertinent results.