We compared the two major protocols for investigating malignant hyperthermia susceptibility. There was 87% accordance in diagnostic outcome. The diverging outcomes were seen in individuals with less reproducible test results near the cutoff limits. In scientific studies, such results should be considered as unknown.

No abstract

Reproducibility of in vitro contracture test results in patients tested for malignant hyperthermia susceptibility.Islander, Gunilla; Ording, H; Bendixen, D; Ranklev Twetman, EvaPublished in: Acta Anaesthesiologica Scandinavica DOI: 10.1034/j.1399-6576.2002.460914.x Published: 2002 Link to publication Citation for published version (APA): Islander, G., Ording, H., Bendixen, D., & Ranklev Twetman, E. (2002). Reproducibility of in vitro contracture test results in patients tested for malignant hyperthermia susceptibility. Acta Anaesthesiologica Scandinavica, 46(9), 1144 -1149 . DOI: 10.1034 /j.1399 -6576.2002 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal Department of Anaesthesiology, Herlev Hospital, University of Copenhagen, DenmarkBackground: The in vitro contracture test (IVCT) is the golden standard to diagnose malignant hyperthermia susceptibility (MHS). A high reproducibility is important for a high validity of a test. Methods: We have therefore analyzed IVCT in 838 patients, investigated in two laboratories. Each halothane and caffeine test was performed in two muscle strips. The test results were analyzed with respect to reproducibility of abnormal outcomes within pairs of tested muscle strips and size of contractures, thresholds and quality criteria. The patients were tested according to the European Malignant Hyperthermia Group protocol (EMHG). To fulfill quality criteria in the EMHG protocol the twitch height should be 10 mN (1 g) or more. For the caffeine test a minimum contracture of 50 mN (5 g) or more at 32 mmol l ª1 caffeine could be used as an alternative quality criterion Results: There was better reproducibility with larger contractures. The correlation between size of contractures and fraction of muscle strips with abnormal contractures was 0.77 or larger. Contractures Ͻ 5 mN (0.5 g) were reproducible in less than half

The ryanodine receptor 1 (RYR1) mutation C1840T has been reported to segregate with malignant hyperthermia (MH) susceptibility in several families. We have investigated several Scandinavian MH families with respect to five different RYR1 mutations reported to cause predisposition to MH, and we here report on two of the families in which the C1840T mutation was detected. In these two families there was recombination between MH susceptibility and this mutation in one and three individuals, respectively. These findings may suggest that it is necessary to reconsider the specificity of the IVCT and the role of C1840T as a cause of MH susceptibility in some families exhibiting this mutation.

In this material the reproducibility of the IVCT was found to be satisfactory.