title: Wheezing on maximal forced exhalation in the diagnosis of atypical asthma. Lack of sensitivity and specificity.
abstract: OBJECTIVE
  To determine whether wheezing on maximal forced exhalation is a predictor of asthma in persons with normal or nearly normal baseline spirometry.
  
  
  METHODS
  Prospective study of patients referred for methacholine challenge testing.
  
  
  METHODS
  Pulmonary function laboratory at a hospital.
  
  
  METHODS
  Forty-four patients referred for methacholine challenge testing because of the clinical suspicion of cough variant or otherwise difficult to diagnose asthma, with normal or nearly normal baseline spirometry and without wheezing on routine lung auscultation during quiet breathing.
  
  
  METHODS
  We listened for wheezing on maximal forced exhalation. Wheezing was defined as a continuous sound with a musical quality. Methacholine challenge testing was done. The concentration of methacholine required to produce a 20% fall in baseline FEV1 (PC20) of less than 8 mg/mL was considered a positive test for asthma.
  
  
  RESULTS
  Wheezing was present on maximal forced exhalation in 8 of 14 patients with a positive methacholine challenge test (sensitivity = 57%) and absent in 11 of 30 patients with a negative test (specificity = 37%). Furthermore, wheezing on maximal forced exhalation was present in 13 of 27 patients with a PC20 greater than 16 mg/mL and absent in 2 of 7 with a PC20 less than 4 mg/mL.
  
  
  CONCLUSIONS
  Wheezing on maximal forced exhalation is neither sensitive nor specific for airway hyperreactivity.
authors.affiliation: Massachusetts General Hospital, Boston.
authors.forename: D K
authors.initials: DK
authors.lastname: King
authors.forename: B T
authors.initials: BT
authors.lastname: Thompson
authors.forename: D C
authors.initials: DC
authors.lastname: Johnson
mesh_terms: D000328:Adult; D001249:Asthma / Q000150:complications / Q000175:diagnosis*; D001985:Bronchial Provocation Tests; D005260:Female; D006801:Humans; D008297:Male; D016210:Methacholine Chloride; D008688:Methacholine Compounds; D008875:Middle Aged; D011446:Prospective Studies; D012119:Respiration; D012129:Respiratory Function Tests; D012135:Respiratory Sounds / Q000209:etiology*; D012680:Sensitivity and Specificity; D013147:Spirometry
chemical_list: D008688:Methacholine Compounds; D016210:Methacholine Chloride