[Study on dynamic changes of airway hyperresponsiveness in children with cough variant asthma]

To explore the dynamic changes of airway hyperresponsiveness (AHR) in children with cough variant asthma (CVA).

A prospective observational study was conducted at the Children's Hospital of Soochow University from April 2012 to March 2013. A total of 36 patients were diagnosed as CVA. According to the integral dose of histamine resulting in a 20% (PD20) fall in forced expiratory volume in 1 s (FEV1), the severity of CVA was graded. Corresponding treatment was administered and the dynamic changes of airway hyperresponsiveness were followed for 0, 1 and 6 months.

Among them, 14 patients suffered from CVA only while another 22 cases had CVA plus upper airway cough syndrome (UACS). PD20 of CVA and CVA+UACS groups were (0.46 ± 0.26) and (0.58 ± 0.34) mg respectively. No statistically significance existed between two groups (t = -0.880, P > 0.05). According to the value of PD20, AHR in CVA patients was classified into four degrees of severe, moderate, mild and very mild. Initially there were moderate (n = 8), mild (n = 21) and very mild (n = 5). At 1 month follow-up, moderate (n = 1), mild (n = 28) and borderline (n = 7); At 6 month, moderate (n = 2), mild (n = 20) and very mild (n = 7). And 4 cases turned negative and another 3 cases became lost. Cough symptom score and PD20 showed no significant correlation (r = -0.086, P > 0.05).

AHR in CVA patients is predominantly mild and very mild. And it decreases rapidly mostly during initial treatment phase. The proportion of conversion from CVA into negative and typical bronchial asthma is relatively low.