title: Methacholine challenge testing: comparison of the two American Thoracic Society-recommended methods.
abstract: OBJECTIVE
  Recent American Thoracic Society guidelines recommend two different methods of methacholine challenge testing: the 2-min tidal breathing method with twofold increases in concentration, and the five-breath dosimeter method with fourfold increases. Since the tidal breathing method delivers more methacholine to the mouthpiece, we hypothesized that the provocative concentration of methacholine required to decrease FEV(1) by 20% (PC(20)) would be lower than with the dosimeter method.
  
  
  METHODS
  Twelve subjects 18 to 45 years old with stable asthma were selected on the basis of a screening PC(20) (by tidal breathing) of < 1 mg/mL, 1 to 4 mg/mL, or 4 to 16 mg/mL (4 subjects in each concentration range). On subsequent visits within a 7-day period, methacholine challenge testing with tidal breathing or dosimeter were performed on separate days, in a randomized crossover manner.
  
  
  RESULTS
  The geometric mean PC(20) was 1.8 mg/mL (95% confidence interval [CI], 0.7 to 4.3) after tidal breathing and 1.6 mg/mL (95% CI, 0.7 to 3.7) after dosimeter (p = 0.2). There was no significant difference between the screening PC(20) and the PC(20) obtained by either method on randomized study days. The maximum decrease in FEV(1) from diluent baseline after the last concentration was 27.8% (range, 20 to 50%) during tidal breathing and 27.9% (range, 16 to 47%) during the dosimeter method (p = 0.35).
  
  
  CONCLUSIONS
  Both methods give similar results. Fourfold increases in methacholine concentration with the dosimeter method are as safe as twofold increases with the tidal breathing method.
authors.affiliation: Pulmonary Division, Department of Pediatrics, College of Medicine, University of Florida, Gainesville, FL, USA. Catherine.wubbel@spectrum-health.org
authors.forename: Catherine
authors.initials: C
authors.lastname: Wubbel
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Asmus
authors.forename: Gary
authors.initials: G
authors.lastname: Stevens
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Chesrown
authors.forename: Leslie
authors.initials: L
authors.lastname: Hendeles
mesh_terms: D000280:Administration, Inhalation; D000293:Adolescent; D000328:Adult; D018927:Anti-Asthmatic Agents / Q000627:therapeutic use; D001249:Asthma / Q000175:diagnosis* / Q000188:drug therapy / Q000503:physiopathology*; D016535:Bronchial Hyperreactivity / Q000175:diagnosis*; D001985:Bronchial Provocation Tests; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D008297:Male; D016210:Methacholine Chloride / Q000494:pharmacology*; D008875:Middle Aged; D011336:Probability; D011379:Prognosis; D011659:Pulmonary Gas Exchange; D012129:Respiratory Function Tests; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D012955:Societies, Medical
chemical_list: D018927:Anti-Asthmatic Agents; D016210:Methacholine Chloride