THE SENSITIVITY AND SPECIFICITY OF THE CAFFEINE-HALOTHANE CONTRACTURETEST - A REPORT FROM THE NORTH-AMERICAN MALIGNANT HYPERTHERMIA REGISTRY

Background: The caffeine-halothane contracture test (CHCT) is the only recognized laboratory test to diagnose malignant hyperthermia (MH). T he authors report the results of their analysis of pooled data from th e North American Malignant Hyperthermia Registry database to determine the sensitivity and specificity of the CHCT. Methods: The MH CLinical Grading Scale was used to identify 32 case subjects who mere ''almost certain'' to be MN susceptible based on clinical criteria alone. Thei r CHCT results were compared with those of a group of 120 control subj ects considered to be at low risk for MH, Diagnostic thresholds of the CHCT were adjusted, and its component tests were combined to generate receiver operating characteristic curves. The maximal Youden index fo r each component test was chosen as the diagnostic threshold indicativ e of MH susceptibility. Results: The highest sensitivity (97%; 95% CI, 84-100%) was achieved with a two-component test with thresholds of gr eater than or equal to 0.5 g contracture for 3% halothane, greater tha n or equal to 0.3 g contracture at 2 mar caffeine, or both, considered positive for MH. The test specificity was 78% (95% CI, 69-85%). The a ddition of other CHCT component tests did not improve CHCT sensitivity or specificity. Conclusion: The CHCT achieves high sensitivity and ac ceptable specificity as a clinical laboratory diagnostic test when it is performed according to published standards, However, it cannot be u sed as a screening test because of the low prevalence of MH in the gen eral population.