Synthesis of research findings has a long-standing
tradition in science. While synthesis is currently required in the US
food and drug regulatory process, formal meta-analysis may substitute
for a pivotal study or broaden the generalizability of drug efficacy
through a preplanned meta-analysis. Preplanned meta-analysis of
individual trials with deliberately introduced heterogeneity may
maximize the generalizability of results from randomized trials.
Combining observational data may help to support an alternative claim
or to quantify adverse events. In this setting, methods to address
potentially greater sources of bias are required. Overall,
meta-analysis adds evidence through the synthesis study findings and
permits examination of how treatment effects vary across of subgroups,
such as age and sex, and across study settings.