Meta-analysis: Neither quick nor easy.

Background: Meta-analysis is often considered to be a simple way to summarize the existing literature. In this paper we describe how a meta-analysis resembles a conventional study, requiring a written protocol with design elements that parallel those of a record review. Methods: The paper provides a structure for creating a meta-analysis protocol. Some guidelines for measurement of the quality of papers are given. A brief overview of statistical considerations is included. Four papers are reviewed as examples. The examples generally followed the guidelines we specify in reporting the studies and results, but in some of the papers there was insufficient information on the meta-analysis process. Conclusions: Meta-analysis can be a very useful method to summarize data across many studies, but it requires careful thought, planning and implementation. [ABSTRACT FROM AUTHOR]