Figure 1. Effect of pretest probability (PTP) on positive predictive value (PPV), negative predictive value (NPV), and efficiency of diagnostic muscle biopsy contracture testing for malignant hyperthermia (MH) susceptibility. Separate graphs are shown for (A) the North American Malignant Hyperthermia Registry (NAMHR) Caffeine-Halothane Contracture Test (CHCT), (B) the European MH Group (EMHG) in vitro contracture test (IVCT), and (C) the alternative “specific” interpretation of the EMHG IVCT in which MHE is considered nondiagnostic. The graph of equivocal predictive value (EPV) shows that MHE alone is not a good diagnostic indicator.