Exploring heterogeneity in meta-analysis: Is the L'Abbe plot useful?

By using a published meta-analysis as an example, this paper discusses the use of L'Abbe plot for investigating the potential sources of heterogeneity in mete-analysis. As compared with other graphic procedures, the L'Abbe pl ot is useful to identify not only the studies having different results from other studies, but also the study arms that are responsible for such diffe rences. This may be important for determining the focus of heterogeneity in vestigations. Results of stochastic simulation indicate that, purely becaus e of random variation, studies with event rates of around 50% are more like ly to be identified as outliers in a L'Abbe plot. This paper also demonstra tes that different methods may identify different trials as "outliers" in m eta analysis. J CLIN EPIDEMIOL 52;8:725-730, 1999. (C) 1999 Elsevier Scienc e Inc.