Capsaicin cough sensitivity and the association with clinical parameters in bronchiectasis.

BACKGROUND: Cough hypersensitivity has been common among respiratory diseases. OBJECTIVE: To determine associations of capsaicin cough sensitivity and clinical parameters in adults with clinically stable bronchiectasis. METHODS: We recruited 135 consecutive adult bronchiectasis patients and 22 healthy subjects. History inquiry, sputum culture, spirometry, chest high-resolution computed tomography (HRCT), Leicester Cough Questionnaire scoring, Bronchiectasis Severity Index (BSI) assessment and capsaicin inhalation challenge were performed. Cough sensitivity was measured as the capsaicin concentration eliciting at least 2 (C2) and 5 coughs (C5). RESULTS: Despite significant overlap between healthy subjects and bronchiectasis patients, both C2 and C5 were significantly lower in the latter group (all P<0.01). Lower levels of C5 were associated with a longer duration of bronchiectasis symptoms, worse HRCT score, higher 24-hour sputum volume, BSI and sputum purulence score, and sputum culture positive for P. aeruginosa. Determinants associated with increased capsaicin cough sensitivity, defined as C5 being 62.5 µmol/L or less, encompassed female gender (OR: 3.25, 95%CI: 1.35-7.83, P<0.01), HRCT total score between 7-12 (OR: 2.57, 95%CI: 1.07-6.173, P = 0.04), BSI between 5-8 (OR: 4.05, 95%CI: 1.48-11.06, P<0.01) and 9 or greater (OR: 4.38, 95%CI: 1.48-12.93, P