Features of cough variant asthma and classic asthma during methacholine-induced brochoconstriction: a cross-sectional study

Cough

Table 1 Patients' characteristics

	Classic asthma	Cough variant asthma	p-value
	n = 58	n = 55
Age (yr)	44.4 ± 15.9	43.2 ± 16.5	0.71
Male/Female (No)	29/29	33/22	0.29
Disease duration at diagnosis (yr)	6.7 ± 10.0	2.8 ± 4.4	0.10
Current smoking (Yes, %)	19.0	5.2	0.029
Atopic status* (Yes, %)	71.4	67.9	0.69
Blood eosinophils (number/μl)	389 ± 247	310 ± 404	0.011
FEV₁ (% predicted)	86.8 ± 19.2	92.1 ± 17.6	0.14
FEV₁/FVC (%)	72.6 ± 11.3	81.8 ± 8.9	< 0.0001
Baseline Rrs (cm H₂O/L/sec)	4.3 ± 2.0	4.0 ± 3.2	0.040
Log Dmin (units)	-0.20 ± 0.82	0.36 ± 0.60	< 0.0001
SRrs (cm H₂O/L/sec/min)	2.9 ± 3.2	2.1 ± 2.1	0.042
Log C5 (μM)	1.51 ± 0.79 (n = 18)	1.17 ± 0.71 (n = 22)	0.15

Values are given as the means ± SD.
*: measured in 56 patients with classic asthma and 53 patients with cough variant asthma. Patients were considered atopic when 1 or more specific IgE antibodies were positive for cat dander, dog dander, weed, grass pollen, mold, or house dust mite.
Abbreviation: Rrs, respiratory resistance. Dmin, cumulative dose of inhaled methacholine at the inflection point, where which respiratory resistance begins to increase. SRrs, slope of the methacholine dose-response curve for Rrs. C5, cough threshold, the lowest concentration of capsaicin that induces 5 or more cough.