title: Predictive value of nonspecific bronchial responsiveness in occupational asthma.
abstract: BACKGROUND
  The diagnosis of occupational asthma (OA) can be challenging and needs a stepwise approach. However, the predictive value of the methacholine challenge has never been addressed specifically in this context.
  
  
  OBJECTIVE
  We sought to evaluate the sensitivity, specificity, and positive and negative predictive values of the methacholine challenge in OA.
  
  
  METHODS
  A Canadian database was used to review 1012 cases of workers referred for a suspicion of OA between 1983 and 2011 and having had a specific inhalation challenge. We calculated the sensitivity, specificity, and positive and negative predictive values of methacholine challenges at baseline of the specific inhalation challenge, at the workplace, and outside work.
  
  
  RESULTS
  At baseline, the methacholine challenge showed an overall sensitivity of 80.2% and a specificity of 47.1%, with positive and negative predictive values of 36.5% and 86.3%, respectively. Among the 430 subjects who were still working, the baseline measures displayed a sensitivity of 95.4%, a specificity of 40.1%, and positive and negative predictive values of 41.1% and 95.2%, respectively. Among the 582 subjects tested outside work, the baseline measures demonstrated a sensitivity and specificity of 66.7% and 52%, respectively, and positive and negative predictive values of 31.9% and 82.2%, respectively. When considering all subjects tested by a methacholine challenge at least once while at work (479), the sensitivity, specificity, and positive and negative predictive values were 98.1%, 39.1%, and 44.0% and 97.7%, respectively.
  
  
  CONCLUSIONS
  A negative methacholine challenge in a patient still exposed to the causative agent at work makes the diagnosis of OA very unlikely.
authors.affiliation: Department of Chest Medicine, Hôpital du Sacré-Coeur de Montreal, University of Montreal, Montreal, Quebec, Canada; Institute for Work and Health, Epalinges-Lausanne, Switzerland; Division of Pulmonary Diseases, Geneva University Hospitals, Geneva, Switzerland. Electronic address: jacques.pralong@chuv.ch.
authors.forename: Jacques A
authors.initials: JA
authors.lastname: Pralong
authors.affiliation: Department of Chest Medicine, Hôpital du Sacré-Coeur de Montreal, University of Montreal, Montreal, Quebec, Canada.
authors.forename: Catherine
authors.initials: C
authors.lastname: Lemière
authors.affiliation: Division of Pulmonary Diseases, Geneva University Hospitals, Geneva, Switzerland.
authors.forename: Thierry
authors.initials: T
authors.lastname: Rochat
authors.affiliation: Department of Chest Medicine, Hôpital du Sacré-Coeur de Montreal, University of Montreal, Montreal, Quebec, Canada.
authors.forename: Jocelyne
authors.initials: J
authors.lastname: L'Archevêque
authors.affiliation: Department of Chest Medicine, Hôpital du Sacré-Coeur de Montreal, University of Montreal, Montreal, Quebec, Canada.
authors.forename: Manon
authors.initials: M
authors.lastname: Labrecque
authors.affiliation: Department of Chest Medicine, Hôpital du Sacré-Coeur de Montreal, University of Montreal, Montreal, Quebec, Canada.
authors.forename: André
authors.initials: A
authors.lastname: Cartier
mesh_terms: D000328:Adult; D059366:Asthma, Occupational / Q000175:diagnosis* / Q000503:physiopathology*; D001985:Bronchial Provocation Tests; D002170:Canada; D016208:Databases, Factual; D005260:Female; D006801:Humans; D008297:Male; D016210:Methacholine Chloride; D008875:Middle Aged; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012307:Risk Factors; D012680:Sensitivity and Specificity
chemical_list: D016210:Methacholine Chloride
keywords: Bronchial responsiveness; methacholine challenge; occupational asthma