Comparative analysis of in vitro contracture tests with ryanodine and a combination of ryanodine with either halothane or caffeine: a comparative investigation in malignant hyperthermia.
BACKGROUND
The diagnosis of susceptibility to malignant hyperthermia (MH) is currently performed on muscle biopsies subjected to halothane-caffeine in vitro contracture tests (IVCTs). There is a consensus on our need to improve the diagnostic potential of IVCTs if we are to maximize the information available for research and diagnosis in MH. This study was designed as a pilot comparative study and we aimed at comparing the ryanodine test and new tests using a combination of ryanodine, halothane and caffeine.


METHODS
One hundred and thirty-two subjects (52 MHS and 80 MHN) were included in this study and new IVCTs were performed in additional muscle biopsy specimens. The contracture time-course was compared considering the onset time of contracture (OT) and the time to reach a 10 mN contracture (10T). Cut-off values were determined using ROC analyses.


RESULTS
For the ryanodine test, sensitivity and specificity calculated for OT were 84.6% and 90.4%, respectively, and were better than those obtained using 10T. Combined tests using either caffeine and ryanodine or halothane and ryanodine did provide higher sensitivities (from 85.3 to 93.9%). A better specificity was only observed for the IVC tests combining halothane (cumulated) and caffeine both with ryanodine (93.9% for both). The largest sensitivity was observed when halothane was used as a bolus and combined with ryanodine. The specificity was always larger with the combined tests as compared to the test using ryanodine alone (from 79.1 to 90.9%). This superiority was confirmed, at least in part, when comparing genetic investigations and the results of new tests in a subgroup of subjects.


CONCLUSIONS
This pilot study showed a clear diagnostic potential for new IVC tests combining halothane, the triggering agent of MH, and ryanodine acting at the calcium release channel, and should be considered as a first step in the investigation of combined tests.
Centre de Résonance Magnétique Biologique et Médicale, Faculté de Médecine, Marseille, France. david.bendahan@medecine.university-mrs.fr
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D
Bendahan
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Guis
N
N
Monnier
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Kozak-Ribbens
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J
Lunardi
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Ghattas
J-P
JP
Mattei
P J
PJ
Cozzone
D018685:Anesthetics, Inhalation; D002110:Caffeine; D004247:DNA / Q000235:genetics; D006221:Halothane; D006801:Humans; D066298:In Vitro Techniques; D008305:Malignant Hyperthermia / Q000175:diagnosis* / Q000235:genetics / Q000503:physiopathology; D009119:Muscle Contraction / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects*; D009154:Mutation / Q000235:genetics; D010726:Phosphodiesterase Inhibitors; D011237:Predictive Value of Tests; D012372:ROC Curve; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012433:Ryanodine
D018685:Anesthetics, Inhalation; D010726:Phosphodiesterase Inhibitors; D012433:Ryanodine; D002110:Caffeine; D004247:DNA; D006221:Halothane