Characteristics of airway hyperresponsiveness in children with chronic cough of different causes

Abstract

To study the characteristics of airway hyperresponsiveness in children with different causes of chronic cough. A prospective study was conducted in children suffering from chronic cough caused by a single reason at the department of respirology of Children's Hospital of Soochow University from April 2012 to December 2013. Bronchial provocation test, induced sputum eosinophil count, and exhale nitric oxide were detected at beginning and 4 weeks later. The severity of the CVA was classified according to the integral dose of histamine which resulted in a 20% (PD20) fall in forced expiratory volume in 1 s (FEV1). All patients received treatment according to the recommended guidelines for chronic cough in children of China. According to the responses to the treatment and the results of physical examinations and laboratory findings, a final diagnosis was confirmed. A total of 66 children were enrolled in this study, including cough variant asthma (CVA)in 17, upper airway cough syndrome (UACS) in 37, and post infection cough (PIC) in 12 cases. Positive AHR in CVA, UACS, and PIC groups was found in 17, 13, and 9 cases respectively at the first visit, and after 4 weeks, it was found in 17, 5, and 2 cases respectively. The severity of AHR in CVA, UACS and PIC at beginning and after 4 weeks were moderate to severe in 5, 0, 0 cases and 1, 0, 0 case; Mild to very mild in 12, 13, 9 cases and 16, 5, 2 cases.Negative response was found in 0, 24, 3 cases and 0, 32, 10 cases, respectively. The values of PD20 in CVA group (0.47 ± 0.28) mg were statistically lower those in UACS group (1.8 ± 0.64) mg and PIC group (1.2 ± 0.80) mg (P < 0.01) . The sputum eosinophil count was > 3% in all cases of CVA but all <3% in UACS and PIC.FeNO and sputum eosinophil counts were positively correlated (r = 0.687, P = 0.000) . The characteristics of airway responsiveness of chronic cough caused by different causes were varied in different AHR severity and course. Bronchial provocation test combined with induced sputum showed certain values for confirming the cause of chronic cough in children.