Serum creatine kinase level as a screening test for susceptibility to malignant hyperthermia.

One hundred thirty-one patients who were referred for muscle biopsy for in vitro contracture testing (IVCT) for susceptibility to malignant hyperthermia (MH) were studied. Serum creatine kinase (CK) levels were determined routinely before biopsy by the hospital clinical laboratories. Thirty-four had abnormal IVCTs (indicating susceptibility to MH) and 87 patients had normal IVCTs; all these 121 patients had normal CK levels. Ten additional patients had other muscle disorders (central core disease, hyperkalemic periodic paralysis, and Duchenne's muscular dystrophy) and abnormal IVCTs; six of the ten had elevated CK levels. We conclude that the serum CK level, as determined routinely, does not identify MH-susceptible individuals, but may indicate the presence of muscle disease. Therefore, the use of serum CK level as a screening or diagnostic test for susceptibility to MH should be abandoned.