title: Reference values for methacholine reactivity (SAPALDIA study).
abstract: BACKGROUND
  The distribution of airway responsiveness in a general population of non-smokers without respiratory symptoms has not been established, limiting its use in clinical and epidemiological practice. We derived reference equations depending on individual characteristics (i.e., sex, age, baseline lung function) for relevant percentiles of the methacholine two-point dose-response slope.
  
  
  METHODS
  In a reference sample of 1567 adults of the SAPALDIA cross-sectional survey (1991), defined by excluding subjects with respiratory conditions, responsiveness during methacholine challenge was quantified by calculating the two-point dose-response slope (O'Connor). Weighted L1-regression was used to estimate reference equations for the 95th , 90th , 75th and 50th percentiles of the two-point slope.
  
  
  RESULTS
  Reference equations for the 95th , 90th , 75th and 50th percentiles of the two-point slope were estimated using a model of the form a + b* Age + c* FEV1 + d* (FEV1)2 , where FEV1 corresponds to the pre-test (or baseline) level of FEV1. For the central half of the FEV1 distribution, we used a quadratic model to describe the dependence of methacholine slope on baseline FEV1. For the first and last quartiles of FEV1, a linear relation with FEV1 was assumed (i.e., d was set to 0). Sex was not a predictor term in this model. A negative linear association with slope was found for age. We provide an Excel file allowing calculation of the percentile of methacholine slope of a subject after introducing age--pre-test FEV1--and results of methacholine challenge of the subject.
  
  
  CONCLUSIONS
  The present study provides equations for four relevant percentiles of methacholine two-point slope depending on age and baseline FEV1 as basic predictors in an adult reference population of non-obstructive and non-atopic persons. These equations may help clinicians and epidemiologists to better characterize individual or population airway responsiveness.
authors.affiliation: Service of Pulmonology, University Hospital Lausanne, Switzerland. pierre-yves.jayet@chuv.hospvd.ch
authors.forename: Pierre-Yves
authors.initials: PY
authors.lastname: Jayet
authors.forename: Christian
authors.initials: C
authors.lastname: Schindler
authors.forename: Nino
authors.initials: N
authors.lastname: Künzli
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Zellweger
authors.forename: Otto
authors.initials: O
authors.lastname: Brändli
authors.forename: André Paul
authors.initials: AP
authors.lastname: Perruchoud
authors.forename: Roland
authors.initials: R
authors.lastname: Keller
authors.forename: Joel
authors.initials: J
authors.lastname: Schwartz
authors.forename: Ursula
authors.initials: U
authors.lastname: Ackermann-Liebrich
authors.forename: Philippe
authors.initials: P
authors.lastname: Leuenberger
mesh_terms: D017677:Age Distribution; D000465:Algorithms; D001985:Bronchial Provocation Tests / Q000379:methods / Q000592:standards*; D003936:Diagnosis, Computer-Assisted / Q000379:methods* / Q000592:standards*; D006801:Humans; D016210:Methacholine Chloride; D012016:Reference Values; D015203:Reproducibility of Results; D012130:Respiratory Hypersensitivity / Q000175:diagnosis* / Q000453:epidemiology*; D012680:Sensitivity and Specificity; D017678:Sex Distribution; D013557:Switzerland / Q000453:epidemiology
chemical_list: D016210:Methacholine Chloride