Bronchial asthma is characterized by a reversible airway obstruction, airway hyperresponsiveness, and eosinophilic airway inflammation. The bronchodilator response(BDR) after short acting beta agonist inhalation and PC20 with methacholine inhalation are frequently used for diagnosing bronchial asthma, However, the relationship between the presence of a bronchodilator response and the degree of airway hyperresponsiveness is uncertain. Therefore, the availability of a eosinophil cationic protein(ECP) and a correlation ECP with a bronchodilator response and airway hyperresposiveness was investigated.

A total 71 patients with a moderate to severe degree of bronchial asthma were enrolled and divided into two groups. 31 patients with a positive bronchodilator response and 38 patients with a negative bronchodilator response were evaluated. In both groups, the serum ECP, peripheral blood eosinophil counts, and total IgE level were measured and the methacholine bronchial provocation test was examined.

There were no differences observed in age, sex, atopy, and baseline spirometry in both groups. The peripheral eosinophil counts showed no difference in both groups, but the ECP level in group 1 (bronchodilator responder group) was higher than in group 2(non-bronchodilator responder group) (22.4±20.7 vs 14.2±10.4, mean±SD). The PC20 in group 1 was significantly lower than in group 2 (1.14±1.68 vs 66±2.98). There was a significant positive correlation between the BDR and ECP, and a negative correlation between the bronchial hyperresponsiveness and ECP.

The bronchodilator response significantly correlated with the bronchial hyperresponsiveness and serum ECP in the moderate to severe asthma patients. Hence, the positive bronchodilator response is probably related with active bronchial inflammation and may be used as a valuable index in treatment, course and prognosis of bronchial asthma.