Abstract
Background: Capsaicin cough challenge is used in pre-clinical and clinical studies to evaluate mechanisms, however standard methods and endpoints discriminate poorly between healthy volunteers (HV) and refractory chronic cough (RCC) patients.
Aims: We aimed to assess the ability of capsaicin dose response curves to differentiate RCC from HV using receiver operator characteristic (ROC) curve analysis.
Methods: 93 HV (median age 39yrs (IQR 29-52), 47 females) and 51 RCC (age 59yrs (53-67), 31 females) performed a full dose response cough challenge, inhaling doubling doses of capsaicin (0.48-1000µmol/L) four times up to the maximum tolerated dose. The number of coughs evoked in 15s following inhalation was recorded. Emax (maximum number of coughs evoked by any dose) and ED50 (dose evoking at least half of the Emax) were derived.
Results: Emax was significantly higher in the RCC group compared with HV (median(IQR) 27(21-37) coughs vs. 13(9-19), p<0.001) and ED50 was significantly reduced (median(IQR) 15.6(3.9-31.3) vs. 31.3(15.6-125.0), p=0.001). These endpoints were significantly influenced by gender (females, higher Emax/lower ED50) but not by age, BMI, lung function. Area under the curve values suggested Emax (0.83, 95%CI 0.75-0.90) was superior to ED50 (0.66, 95%CI 0.57-0.76) (Fig1).
Conclusion: ROC curve analysis suggests capsaicin evoked Emax discriminates well between RCC and HV therefore showing promise as a diagnostic test for RCC.
Footnotes
Cite this article as: European Respiratory Journal 2020; 56: Suppl. 64, 4561.
This abstract was presented at the 2020 ERS International Congress, in session “Respiratory viruses in the "pre COVID-19" era”.
This is an ERS International Congress abstract. No full-text version is available. Further material to accompany this abstract may be available at www.ers-education.org (ERS member access only).
- Copyright ©the authors 2020
