Table 1—

Subject characteristics and effect of methacholine challenge tests

AsthmaticNonasthmaticp‐value
Subjects n2518
M:F14:115:130.12#
Age yrs46.5±5.933.7±5.60.001
Atopic21 (85%)7 (42%)0.006#
Exhaled NO ppb24.3 (17.2–34.4)12.4 (9.6–16.1)0.005
FEV1 % predicted83.3±5.799.4±5.3<0.001
Rrs,mean % predicted147.8±17.9111.2±15.90. 007
Baseline tidal volume L0.91±0.090.86±0.090.45
Baseline inspiratory capacity L2.56±0.262.57±0.330.97
DRR % fall FEV1·µmol−114.4 (8.6–22.9)0.26 (0.09–0.44)<<0.001
Methacholine dose µmol1.8 (1.1–3.0)95.5 (54.7–166.6)<<0.001
Increase in Rrs,mean %55.7±13.568.0±22.90.34
Decrease in FEV1 %24.4±2.415.0±3.0<0.001
  • Data are presented as mean±95% confidence interval (CI), geometric means (95% CI), or n (% positive skin-prick tests). p‐Values are for the comparison between groups by unpaired t‐test or Chi-squared test (#)

  • M: male

  • F: female

  • NO: nitric oxide

  • ppb: parts per billion

  • FEV1: forced expiratory volume in one second

  • Rrs,mean: mean of all respiratory system resistance values obtained over 1 min of tidal breathing

  • DRR: dose-response ratio

  • <<: much less than