Issues in meta-analysis: an overview.

A summary is provided for the relevant issues that investigators must address when wishing to synthesize data via a meta-analysis. The analogy is made to conducting a clinical trial and its components. Both design and statistical issues are discussed with the goal of assuring that the proper elements are included in the meta-analysis. Further, global concerns are presented so that the researcher is aware of the clinical controversies faced when conducting a meta-analysis. Finally a comparison is made of the advantages and disadvantages of a large-scale clinical trial versus a meta-analysis.