Static v. dynamic tests in the in vitro diagnosis of malignant hyperthermia susceptibility

In vitro contracture tests, in which muscle specimens are exposed to halothane or caffeine are, at present, the only generally accepted screening methods for the diagnosis of susceptibility to malignant hyperthermia (MHS). Static tests (performed with the muscle held at constant length) are used more commonly although, in addition, some MH investigation units use dynamic tests, in which the length of the specimen is varied. We have performed dynamic and static tests in parallel on muscle from 112 patients. The dynamic halothane test was more sensitive in discriminating between MHS and MH negative (MHN) individuals than the static halothane test. However, the dynamic caffeine test was less sensitive at discriminating between MHS and MHN individuals, and nothing is to be gained by including it in the investigation.