title: Features of cough variant asthma and classic asthma during methacholine-induced brochoconstriction: a cross-sectional study.
abstract: BACKGROUND
  Little is known regarding mechanistic and phenotypic differences between cough variant asthma (CVA), presenting with a chronic cough as the sole symptom that responds to bronchodilators, and classic asthma with wheezing during methacholine inhalation. Here we reported airway sensitivity, airway reactivity, and as the main concern, the appearance of cough and wheezes during methacholine inhalation in patients with CVA or classic asthma.
  
  
  METHODS
  We cross-sectionally examined the degrees of airway sensitivity, the point where resistance started to increase, and reactivity, the slope of the methacholine-resistance curve, and the appearance of cough and wheezes in steroid-naïve adult patients with classic asthma (n = 58) or CVA (n = 55) while they were continuously inhaling methacholine during simultaneous measurement of respiratory resistance.
  
  
  RESULTS
  Patients with CVA were less sensitive and less reactive to inhaled methacholine and wheezed less frequently but coughed more frequently during methacholine-induced bronchoconstriction than did patients with classic asthma. Multivariate analysis revealed that airway hypersensitivity and lower baseline FEV1/FVC were associated with the appearance of wheezes, whereas a diagnosis of CVA was associated with coughing.
  
  
  CONCLUSIONS
  There are mechanistic and phenotypic differences between CVA and classic asthma during methacholine inhalation. Frequent coughing during bronchoconstriction may be a distinctive feature of CVA.
authors.affiliation: Department of Respiratory Medicine, Kyoto University, Kyoto, Japan. hmatsumo@kuhp.kyoto-u.ac.jp
authors.forename: Hisako
authors.initials: H
authors.lastname: Matsumoto
authors.forename: Akio
authors.initials: A
authors.lastname: Niimi
authors.forename: Masaya
authors.initials: M
authors.lastname: Takemura
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Ueda
authors.forename: Masafumi
authors.initials: M
authors.lastname: Yamaguchi
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Matsuoka
authors.forename: Makiko
authors.initials: M
authors.lastname: Jinnai
authors.forename: Kazuo
authors.initials: K
authors.lastname: Chin
authors.forename: Michiaki
authors.initials: M
authors.lastname: Mishima