[Screening tests for malignant hyperthermia susceptibility]

The ideal screening test for malignant hyperthermia susceptibility (MHS) has yet to be discovered. It should be simple noninvasive, yet totally specific and sensitive. Until such an ideal test becomes available, allowing simple routine preoperative screening, tests should only be used in certain specific situations. These include: patients in whom a clinical crisis was suspected; the members of the family of a subject labeled MHS because of a fatal, or otherwise, crisis, or in whom tests were positive; patients with other pathological conditions which could be linked to malignant hyperthermia (MH) (some myopathies, effort or stress MH, neuroleptic malignant syndrome). The various tests proposed in the literature aim at revealing MHN subjects, using or not a triggering agent, halothane most often. However, detecting these abnormalities sometimes gives greater insight into the physiopathology of MH than in the detection of an individual patient's susceptibility. The tests have been classified as in vivo, electrophysiological, blood, and in vitro muscle biochemical, morphological, and pharmacological tests. The discovery of new tests gives renewed hope: CPK levels, platelet tests, calcium sarcoplasmic reticular reuptake, lymphocyte Quin 2 test, nuclear magnetic resonance spectroscopy. However, experts worldwide agree that the only reference test to this day remains the in vitro halothane caffeine contracture tests. These tests have shown their reliability; they must be performed on muscle strips obtained from surgically removed muscle biopsies, by laboratories used to this technique and who have at their disposal a sufficiently large group of MHS subjects with a clear-cut clinical crisis, as well as controls. The patients must therefore travel to these laboratories. The design of common protocols for European laboratories on one hand, and the North American laboratories on the other, is a good guarantee of the reliability of these tests.