Meta-analysis of Cohen's kappa

Cohen's kappa is the most important and most widely accepted measure of inter-rater reliability when the outcome of interest is measured on a nominal scale. The estimates of Cohen's kappa usually vary from one study to another due to differences in study settings, test properties, rater characteristics and subject characteristics. This study proposes a formal statistical framework for meta-analysis of Cohen's kappa to describe the typical inter-rater reliability estimate across multiple studies, to quantify between-study variation and to evaluate the contribution of moderators to heterogeneity. To demonstrate the application of the proposed statistical framework, a meta-analysis of Cohen's kappa is conducted for pressure ulcer classification systems. Implications and directions for future research are discussed.