Predictors for typical asthma onset from cough variant asthma.

Cough variant asthma is recognized to be a precursor of asthma or preasthmatic state because nearly 30% patients with cough variant asthma develop typical asthma within several years. However, predictors for risk of typical asthma onset from cough variant asthma are unknown. Forty-one patients with cough variant asthma (median age 50 years, 13 men and 28 women), who had undertaken spirometry, bronchial reversibility test, methacholine provocation test, measurements of peripheral blood eosinophil count, serum total IgE, and specific IgE to common allergens, and induced sputum eosinophil count at presentation, were followed up with special emphasis on typical asthma onset during 1 year or more (median 4 years, range 1-12.4). Long-term inhaled corticosteroids (ICS) were taken in 27 patients. Univariate and multivariate logistic analyses were performed to determine the predictors for typical asthma onset. Asthma onset was recognized in 7 patients. Bronchial hyperresponsiveness, peripheral blood eosinophil count, and no use of ICS were significant predictors for the typical asthma onset by univariate analysis. However, only bronchial hyperresponsiveness was the significant predictor when multivariate analysis was used (adjusted OR 0.028, 95% CI 0.001-0.783, p = 0.0355). Bronchial hyperresponsiveness may be the most important predictor for risk of typical asthma onset from cough variant asthma.