The caffeine skinned fibre tension test: use for the diagnosis of malignant hyperthermia susceptibility.

Objective: To assess the reactivity of sarcoplasmic reticulum to caffeine, using the skinned muscle fibre tension test and to compare it with the refe rence in vitro contracture test in the diagnosis of malignant hyperthermia (HM) susceptibility. Study designs Laboratory investigation. Materials Muscle biopsies from 63 patients, including 29 classified as susc eptible to MH (MHS) and 34 classified as non-susceptible (MHN) according to criteria of the European and the North American MH groups. Methods The reactivity to caffeine and halothane of skinned muscle fibres w as compared, according to the type of fibres, with the data of the in vitro contracture test. The type of fibres (type I: oxidative, slaw;type II: gly colytic, fast) were determined with strontium dose-response curves. Results: The reactivity to caffeine was significantly lower in the MHS grou p, for both type I and type II skinned fibres. However, in comparison with the data of the in vitro contracture tests, using the ROC curve analysis, t he best sensitivity-specificity compromise was 90%-71% and 74%-84% for type I and type II skinned fibres respectively. Conclusion: The skinned muscle fibre tension test cannot be used instead of the in vitro contracture test for the diagnostic of MHS. However, it may s trengthen the data of the latter. (C) 1999 Elsevier, Paris.