title: Multicentre evaluation of in vitro contracture testing with bolus administration of 4-chloro-m-cresol for diagnosis of malignant hyperthermia susceptibility.
abstract: OBJECTIVE
  The in vitro contracture test with halothane and caffeine is the gold standard for the diagnosis of susceptibility to malignant hyperthermia (MH). However, the sensitivity of the in vitro contracture test is between 97 and 99% and its specificity is 78-94% with the consequence that false-negative as well as false-positive test results are possible. 4-Chloro-m-cresol is potentially a more specific test drug for the in vitro contracture test than halothane or caffeine. This multicentre study was designed to investigate whether an in vitro contracture test with bolus administration of 4-chloro-m-cresol can improve the accuracy of the diagnosis of susceptibility to MH.
  
  
  METHODS
  Three hundred and fifty-two patients from 11 European MH laboratories participated in the study. The patients were first classified as MH susceptible, MH normal or MH equivocal by the in vitro contracture test according to the European MH protocol. Muscle specimens surplus to diagnostic requirements were used in this study (MH susceptible = 103 viable samples; MH equivocal = 51; MH normal = 204). 4-Chloro-m-cresol was added to achieve a concentration of 75 micromol L(-1) in the tissue bath. The in vitro effects on contracture development and muscle twitch were observed for 60 min.
  
  
  RESULTS
  After bolus administration of 4-chloro-m-cresol, 75 micromol L(-1), 99 of 103 MH-susceptible specimens developed marked muscle contractures. In contrast, only two of 204 MH-normal specimens showed an insignificant contracture development following 4-chloro-m-cresol. From these results, a sensitivity rate of 96.1% and a specificity rate of 99.0% can be calculated for the in vitro contracture test with bolus administration of 4-chloro-m-cresol 75 micromol L(-1). Forty-three patients were diagnosed as MH equivocal, but only specimens from 16 patients developed contractures in response to 4-chloro-m-cresol, indicating susceptibility to MH.
  
  
  CONCLUSIONS
  The in vitro contracture test with halothane and caffeine is well standardized in the European and North American test protocols. However, this conventional test method is associated with the risk of false test results. Therefore, an improvement in the diagnosis of MH is needed. Regarding the results from this multicentre study, the use of 4-chloro-m-cresol could increase the reliability of in vitro contracture testing.
authors.affiliation: University Hospital Hamburg-Eppendorf, Department of Anaesthesiology, Hamburg, Germany. wappler@uke.uni-hamburg.de
authors.forename: F
authors.initials: F
authors.lastname: Wappler
authors.forename: M
authors.initials: M
authors.lastname: Anetseder
authors.forename: C P
authors.initials: CP
authors.lastname: Baur
authors.forename: K
authors.initials: K
authors.lastname: Censier
authors.forename: S
authors.initials: S
authors.lastname: Doetsch
authors.forename: P
authors.initials: P
authors.lastname: Felleiter
authors.forename: M
authors.initials: M
authors.lastname: Fiege
authors.forename: R
authors.initials: R
authors.lastname: Fricker
authors.forename: P J
authors.initials: PJ
authors.lastname: Halsall
authors.forename: E
authors.initials: E
authors.lastname: Hartung
authors.forename: J J A
authors.initials: JJ
authors.lastname: Heffron
authors.forename: L
authors.initials: L
authors.lastname: Heytens
authors.forename: P M
authors.initials: PM
authors.lastname: Hopkins
authors.forename: W
authors.initials: W
authors.lastname: Klingler
authors.forename: F
authors.initials: F
authors.lastname: Lehmann-Horn
authors.forename: Y
authors.initials: Y
authors.lastname: Nivoche
authors.forename: V
authors.initials: V
authors.lastname: Tegazzin
authors.forename: I
authors.initials: I
authors.lastname: Tzanova
authors.forename: A
authors.initials: A
authors.lastname: Urwyler
authors.forename: R
authors.initials: R
authors.lastname: Weisshorn
authors.forename: J
authors.initials: J
authors.lastname: Schulte am Esch
mesh_terms: D001706:Biopsy; D002110:Caffeine; D003408:Cresols; D004198:Disease Susceptibility / Q000175:diagnosis; D006221:Halothane; D006801:Humans; D066298:In Vitro Techniques; D008305:Malignant Hyperthermia / Q000175:diagnosis*; D009119:Muscle Contraction / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000503:physiopathology; D012680:Sensitivity and Specificity
chemical_list: D003408:Cresols; C006984:chlorocresol; D002110:Caffeine; D006221:Halothane