A clinical study to determine the threshold of bronchodilator response for diagnosing asthma in Chinese children

BACKGROUND: There is few objective, clinically feasible and inexpensive test for diagnosing childhood asthma. We want to find an ideal way to solve it. METHODS: The control group was 301 non-asthmatic children, and the asthma group was 286 asthmatic children. The asthmatic children were divided into three groups according to the severity of their disease. Pre- and post-bronchodilator spirometer tests were performed, and the main spirometer parameters were compared. The bronchodilator response (BDR) [BDR is used to determine the reversibility of airway obstruction by measuring the changes of forced expiratory volume in the first second (FEV(1)) before and after inhalation of bronchodilators] was then determined, and the optimal threshold of BDR for diagnosing childhood asthma was found. RESULTS: 301 non-asthmatic children and 286 asthmatic children participated in the study, the demographics were similar. FEV(1) for pre-bronchodilator of asthmatic children was significantly lower than that of non-asthmatic children (P ≤ 0.01). BDR of non-asthmatic children was 3.30 ± 3.85%. BDR of asthmatic children was 9.45 ± 9.15%. There was no significant difference in BDR for patients with different severities of asthma within the group. BDR had no statistical correlation with gender, age, height, weight in neither non-asthmatic children nor asthmatic children. On the receiver-operating characteristic curve, a BDR threshold of ≥ 7.5% offered an optimal balance in asthma diagnosis with a sensitivity rate of 50.7% and specificity rate of 87.7%. Meanwhile, with a BDR threshold of ≥ 12%, the sensitivity rate was 28.7% and the specificity rate was 96.3%. CONCLUSION: A BDR threshold of ≥ 7.5% has more value in childhood asthma diagnosis as compared to ≥ 12%. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s12519-019-00293-9) contains supplementary material, which is available to authorized users.