Development of wheezing in patients with cough variant asthma during an increase in airway responsiveness

ABSTRACT: Two theories explaining the mechanism for the manifestation of cough without wheeze in patients with cough variant asthma (CVA) are either a higher wheezing threshold or a milder degree of airway hyperresponsiveness. A significant proportion of patients diagnosed as having CVA eventually develop wheezing. The aim of this study was to investigate whether this change in the manifestation of asthma was associated with a decrease in wheezing threshold and/or an increase in airway hyperresponsiveness. Thirty-six children (7–15 yrs) with CVA were prospectively studied for 4 yrs. Bron-chial provocation tests with methacholine using the stepwise increasing concentra-tion technique were performed annually to measure the provocative cumulative dose producing a 20 % fall in forced expiratory volume in one second (PD20). Wheezing thresholds were additionally determined at the initiation of and the end of the study (development of wheezing, or after 4 yrs). Sixteen (Group 1) of 29 patients available for the follow-up developed clinical wheezing during the period; 13 patients (Group 2) stayed as CVA or their coug