Systematic reviews and meta-analyses are essential for drawing conclusions regarding etiologic associations between exposures or interventions and health outcomes. Observational studies comprise a substantive source of the evidence base. One major threat to their validity is residual confounding, which may occur when component studies adjust for…

Randomised controlled trials of cancer treatments typically report progression free survival (PFS) and overall survival (OS) outcomes. Existing methods to synthesise evidence on PFS and OS either rely on the proportional hazards assumption or make parametric assumptions which may not capture the diverse survival curve shapes across studies and…

Explores the nature of meta-analysis by placing it in the context of research synthesis. Methods of meta-analysis are described and compared with other forms of research integration, and findings for several meta-analyses are provided to show advantages of quantitative review methods. (SLD)

Some guidelines are offered for interpreting and evaluating meta-analytic reviews of research. The choice of unit of analysis, the issue of fixed versus random effects, the meaning of heterogeneity, the determination of appropriate contrasts, and the choice of measures of central tendency are discussed. (SLD)

The six articles of this issue discuss the place of meta-analysis in the health professions and present two state-of-the-art meta-analyses using a variety of innovative methodologies, statistics, and secondary analytic procedures. A survey conducted for this issue and its sequel explores interventions to facilitate meta-analysis. (SLD)