Clinical features and cough sensitivity of patients with idiopathic chronic cough

Cho, You Sook; Lee, Jae Cheon; Lim, Yeun Jeong; Lee, Eun Young; Shin, Jeong Hyun; Lim, Mi Kyoung; Yoo, Bin; Moon, Hee Bom

Abstract

BACKGROUND: Chronic cough is a common clinical problem to which various etiologies are attributable; postnasal drip, asthma, gastroesophageal reflux (GER) and chronic bronchitis, However, in some cases, no particular etiology can be confirmed.
OBJECTIVE
This study was aimed to evaluate cough sensitivity and the clinical manifestations of patients with idiopathic chronic cough.
MATERIALS AND METHODS
We recruited 70 non-smoking patients who had been coughing for more than 3 weeks without any history, symptoms or signs of rhinitis, sinusitis, typical asthma, GER or recent upper respiratory infection episodes. Nineteen healthy controls were also enrolled. Bronchial provocation tests with methacholine, capsaicin and distilled water (DW) were performed.
RESULTS
Thirteen patients were positive to rnethacholine test (PC20 < 25mg/ml) and defined as cough variant asthma. The others are classified into idiopathic chronic cough. By capsaicin and DW challenge tests, idiopathic cough patients could be divided into two groups, i.e., increased cough sensitivity (ICS) and normal cough sensitivity (NCS) groups. DW- induced cough counts were negatively correlated with C7 (lowest capsaicin concentration inducing continuous 7 or more coughs) (r=-0.739, p<0.001). No difference was found in clinical features such as age, sex, atopy, or peripheral eosinophil counts between these two groups but cough counts per cough burst were significantly higher in the ICS group.
CONCLUSION
The heterogeneity in cough sensitivity of idiopathic chronic cough patients may refiect different pathophysiologic mechanisms. It is unclear whether patients with NCS merely have habitual or psychogenic cough or not. These suggest that different therapentic strategies should be established on idiopathic chronic cough patients according to cough sensitivity.