IN-VITRO CONTRACTURE TEST FOR DIAGNOSIS OF MALIGNANT HYPERTHERMIA FOLLOWING THE PROTOCOL OF THE EUROPEAN MH GROUP - RESULTS OF TESTING PATIENTS SURVIVING FULMINANT MH AND UNRELATED LOW-RISK SUBJECTS

Background: Determination of sensitivity and specificity of the in vit ro contracture test (IVCT) for malignant hyperthermia (MH) susceptibil ity using the European MH Group (EMHG) protocol has been performed in some laboratories but only on a small sample from the combined EMHG. T hus, the purpose of the present study was to determine combined EMHG s ensitivity and specificity of the test. Methods: Results of IVCT of pa tients with previous fulminant MH and normal, low-risk subjects (contr ols) were collected from 22 centres of the EMHG. IVCT was performed ac cording to the EMHG protocol. Patients were included in the study if t he clinical crisis had a score of at least 50 points with the Clinical Grading Scale. Low-risk subjects were included provided they did not belong to a family with known MH susceptibility, they had not develope d any signs of MH at previous anaesthetics, and they did not suffer fr om any neuromuscular disease. For inclusion of both MH patients and lo w-risk subjects, at least 1 muscle bundle in the IVCT should have twit ches of 10 mN (1 g) or more. For evaluation of individual tests, only muscle bundles with twitch heights of 10 mN (1 g) or more were used. R esults: A total of 1502 probands had undergone IVCT because of a previ ous anaesthesia with symptoms and signs suggestive of MH. Of these, 11 9 had clinical scores of 50 and above. From these 119 Mi-I-suspected p atients and from 202 low-risk subjects, IVCT data were collected. Subs equently, 14 MH-suspected patients were excluded from further analysis for the following reasons: In 3 patients, the suspected MH episode co uld be fully explained by diseases other than MH; in 11 MHS patients, IVCT was incomplete (n=1), data were lost (n=3), or none of the muscle bundles fulfilled twitch criteria (n=7). Of the remaining 105 MH-susp ected patients, 89 were MHS, 10 MHEh, 5 MHEc, and one MHN. Thus, we ob served a diagnostic sensitivity of the IVCT of 99.0% if the MHE group is considered susceptible (95% confidence interval 94.8-100.0%). Of th e 202 low-risk subjects, 3 were MHS, 5 MHEh, 5 MHEc, and 189 MHN. This gives a specificity of the IVCT of 93.6% (95% confidence interval 89. 2-96.5%). Conclusion: The IVCT for diagnosis of MH susceptibility in E urope has a high sensitivity and a satisfactory specificity.