title: Reproducibility of allergen-induced early and late asthmatic responses.
abstract: BACKGROUND
  Constant-dose allergen inhalation challenges are frequently used to examine the effect of antiasthma drugs on the allergen-induced early and late asthmatic responses. The end-point measurements in such studies are the maximal early and late percent decreases in the forced expiratory volume in 1 second (FEV1).
  
  
  OBJECTIVE
  Our purpose was to observe the reproducibility and to determine the sample sizes required for such studies.
  
  
  METHODS
  Twenty-eight subjects with allergen-induced early and late responses were studied with two constant-dose allergen challenges separated by 2 to 12 weeks. The early response was measured as the maximum percent decrease in FEV1 during the first 2 hours and the late response as the maximum percent decrease in FEV1 between 3 to 7 hours.
  
  
  RESULTS
  The mean +/- SEM early responses were 23.1% +/- 1.0% and 24.7% +/- 2.0%, whereas the mean late responses were 23.3% +/- 2.0% and 24.5% +/- 2.2%. Reproducibility of measurements were such that fewer than eight subjects are required, to show 50% attenuation of either the early or late response (with 90% power).
  
  
  CONCLUSIONS
  The method of constant-dose allergen challenge is a sensitive tool for detecting changes in early and late asthmatic responses after the use of antiasthma medication.
authors.affiliation: Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: M D
authors.initials: MD
authors.lastname: Inman
authors.forename: R
authors.initials: R
authors.lastname: Watson
authors.forename: D W
authors.initials: DW
authors.lastname: Cockcroft
authors.forename: B J
authors.initials: BJ
authors.lastname: Wong
authors.forename: F E
authors.initials: FE
authors.lastname: Hargreave
authors.forename: P M
authors.initials: PM
authors.lastname: O'Byrne
mesh_terms: D000280:Administration, Inhalation; D000485:Allergens / Q000008:administration & dosage*; D001249:Asthma / Q000139:chemically induced* / Q000188:drug therapy; D006801:Humans
chemical_list: D000485:Allergens