Atopic features of cough variant asthma and classic asthma with wheezing.

BACKGROUND

Cough variant asthma is a phenotype of asthma solely presenting with coughing. It involves airway inflammation and remodelling as does classic asthma with wheezing, and a subset of patients may progress to classic asthma. The atopic features of cough variant asthma remain unclear.

OBJECTIVE

To compare atopic features between patients with cough variant asthma and those with classic asthma, and to examine the possible correlation of these features with the future development of wheezing in the former group.

METHODS

Total and specific IgE levels of seven common aeroallergens [house dust mite (HDM), Gramineae/Japanese cedar/weed pollens, moulds, cat/dog dander] were examined in 74 cough variant asthma patients and in 115 classic asthma patients of varying severity. Forty of the former patients were prospectively observed for 2 years to determine whether cough variant asthma progressed to classic asthma despite inhaled corticosteroid treatment.

RESULTS

Patients with classic asthma had higher total IgE (P<0.0001), larger numbers of sensitized allergens (P=0.03), and higher rates of sensitization to dog dander (24% vs. 3%, P<0.0001), HDM (46% vs. 28%, P=0.02), and moulds (17% vs. 7%, P=0.047) than did patients with cough variant asthma. Wheezing developed in six (15%) patients with cough variant asthma, who were sensitized to larger numbers of allergens (P=0.02) and had higher rates of sensitization to HDM (P=0.01) and dog dander (P=0.02) than the 34 patients in whom wheezing did not develop. Among the patients with classic asthma, total and specific IgE variables were similar in the subgroup with mild disease (n=60) and the subgroup with moderate-to-severe disease (n=55), as reported previously.

CONCLUSIONS

Atopy may be related to the development of wheezing in patients with cough variant asthma. To prevent the progression of cough variant asthma to classic asthma, avoidance of relevant allergens may be essential.