Determinants of asthma control and quality of life in stable asthma: evaluation of two new cough provocation tests

INTRODUCTION: Asthma control and quality of life are poorly associated with traditional asthma biomarkers. OBJECTIVES: In the present study, we evaluated two new cough provocation tests in this respect. METHODS: Asthma Control Questionnaire and Leicester Cough Questionnaire were completed by 36 stable asthmatics. Cough provocation tests with hypertonic saline and isocapnic hyperpnoea of dry air were performed, as well as spirometry, ambulatory peak expiratory flow (PEF) monitoring and exhaled nitric oxide (eNO) measurement. RESULTS: Leicester Cough Questionnaire score correlated closely with cough responsiveness to hypertonic saline and isocapnic hyperpnoea (R = -0.66, P < 0.001 and R = -0.49, P = 0.002, respectively). Asthma Control Questionnaire score also correlated with the cough responsiveness to these tests (R = 0.52, P = 0.001 and R = 0.43, P = 0.008, respectively). Forced expiratory volume in 1 s (%predicted), diurnal PEF variation and eNO did not correlate with cough-related quality of life but showed some association with asthma control. There was a significant correlation between Leicester Cough Questionnaire and Asthma Control Questionnaire (R = -0.54, P = 0.001). CONCLUSIONS: Asthma control and cough-related quality of life are more closely associated with cough responsiveness to the investigated cough provocation tests than to eNO and traditional indices of bronchial obstruction. Cough is a major contributor to poor asthma control.