Expired breath condensate hydrogen peroxide concentration and pH for screening cough variant asthma among chronic cough

The reported studies suggest a role for eosinophils in the pathogenesis of cough variant asthma. In the present study, the expired breath condensate level of hydrogen peroxide and pH were determined in patients with cough variant asthma and compared to subjects with classical asthma, with chronic cough nonasthmatic and healthy control. Twenty-seven patients with cough variant asthma, 43 patients with classical asthma, 32 patients with chronic cough and 27 healthy subjects were studied in a cross-sectional study. Hydrogen peroxide concentration was significantly higher in cough variant asthma as compared to chronic cough nonasthmatic patients and healthy control subjects, while pH level was significantly lower in cough variant asthma as compared to chronic cough nonasthmatic patients and healthy control subjects. However, there was no significant difference in expired breath condensate hydrogen peroxide and pH between cough variant asthma and classical asthma. In conclusion, hydrogen peroxide concentration and pH of expired breath condensate may be used as noninvasive markers to differentiate cough variant asthma from chronic cough.