Meta-analysis of clinical studies of diagnostic tests: developments in how the receiver operating characteristic "works".

Meta-analytic summaries are needed on clinical studies of diagnostic tests. Meta-analyses on clinical studies of diagnostic tests commonly use the receiver operating characteristic method, which differs conceptually and computationally from the more widely known meta-analytic methods applicable in other contexts, such as in studies of randomized controlled trials. Important conceptual differences for clinical studies of diagnostic tests versus randomized controlled trials are that the study subpopulations are not defined by random allocation and the test threshold typically varies across studies to accommodate "rule in" versus "rule out" testing strategies. The receiver operating characteristic method has evolved substantially in the past decade, and the most recent approaches use multilevel regression methods that require iterative computational solutions to estimate the influence of the study-level variables. Using current methodology, a meta-analysis on clinical studies of diagnostic tests can address questions relevant to the clinical application of a diagnostic test that cannot be answered at the level of the individual study.