title: Methacholine dose-response slopes from maximal bronchial challenge tests in asthmatic children: methodological aspects.
abstract: To determine whether the slope of a maximal bronchial challenge test (in which FEV1 falls by over 50%) could be extrapolated from a standard bronchial challenge test (in which FEV1 falls up to 20%), 14 asthmatic children performed a single maximal bronchial challenge test with methacholine (dose range: 0.097-30.08 mumol) by the dosimeter method. Maximal dose-response curves were included according to the following criteria: (1) at least one more dose beyond a delta FEV1 > or = 20%; and (2) a MFEV1 > or = 50%. PD20 FEV1 was calculated, and the slopes of the early part of the dose-response curve (standard dose-response slopes) and of the entire curve (maximal dose-response slopes) were calculated by two methods: the two-point slope (DRR) and the least squares method (LSS) in % delta FEV1 x mumol-1. Maximal dose-response slopes were compared with the corresponding standard dose-response slopes by a paired Student's t test after logarithmic transformation of the data; the goodness of fit of the LSS was also determined. Maximal dose-response slopes were significantly different (p < 0.0001) from those calculated on the early part of the curve: DRR20% (91.2 +/- 2.7 delta FEV1%. mumol-1) was 2.88 times higher than DRR50% (31.6 +/- 3.4 delta FEV1%. mumol-1), and the LSS20% (89.1 +/- 2.8% delta FEV1. mumol-1) was 3.10 times higher than LSS50% (28.8 +/- 1.5% delta FEV1. mumol-1). The goodness of fit of LSS50% was significant in all cases, whereas LSS20% failed to be significant in one. These results suggest that maximal dose-response slopes cannot be predicted from the data of standard bronchial challenge tests.
authors.affiliation: Department of Pathophysiology, Faculty of Medical Sciences, UNL, Lisbon, Portugal.
authors.forename: T
authors.initials: T
authors.lastname: Gamboa
authors.forename: N
authors.initials: N
authors.lastname: Neuparth
authors.forename: I
authors.initials: I
authors.lastname: Ribeiro da Silva
authors.forename: J E
authors.initials: JE
authors.lastname: Pinto
authors.forename: A B
authors.initials: AB
authors.lastname: Rendas
mesh_terms: D000293:Adolescent; D001249:Asthma / Q000175:diagnosis* / Q000503:physiopathology; D016535:Bronchial Hyperreactivity / Q000503:physiopathology*; D001985:Bronchial Provocation Tests / Q000379:methods* / Q000706:statistics & numerical data; D016085:Bronchoconstrictor Agents / Q000008:administration & dosage; D002648:Child; D004305:Dose-Response Relationship, Drug; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D016018:Least-Squares Analysis; D008297:Male; D016210:Methacholine Chloride / Q000008:administration & dosage; D011237:Predictive Value of Tests
chemical_list: D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride