Cough reflex testing with inhaled capsaicin in the study of chronic cough.
OBJECTIVE
To assess the utility of capsaicin test in the differential diagnosis of non-productive causes of chronic cough and to examine the effects of treatment on this reflex.


METHODS
86 healthy volunteers and 101 patients with chronic cough: asthma (n: 54) gastroesophageal reflux (n: 35) and post-nasal drip syndrome (n: 12).


METHODS
Prospective intervention trial. Spirometry, bronchoprovocation test with histamine (PC20), and cough challenge with ascending concentrations of capsaicin (0.49-500 microM) were initially performed in all subjects. Patients were treated for 3 months according to the origin of the cough. Concentrations that elicited two (C2) and five or more coughs (C5) were determined before and after treatment.


RESULTS
In healthy subjects, cough sensitivity to capsaicin was not influenced by gender or smoking status; however, women with chronic cough were more sensitive to cough challenge than men. C2 and C5 were significantly lower in patients with asthma or gastroesophageal reflux than in post-nasal drip syndrome. No significant correlation was observed between the capsaicin cough threshold and PC20. Cough sensitivity did not improve significantly in most patients with asthma or gastroesophageal reflux despite adequate medical treatment during 3 months. Discriminative value of capsaicin test to differentiate healthy subjects from patients with asthma or reflux was poor.


CONCLUSIONS
Cough sensitivity to inhaled capsaicin is a safe and reproducible tool in the study of chronic cough. However, its usefulness for the management and differential diagnosis is limited.
Nieto
L
L
Service of Pneumology and Service of Gastroenterology, Hospital Universitario La Fe, Valencia, Spain.
de Diego
A
A
Perpiñá
M
M
Compte
L
L
Garrigues
V
V
Martínez
E
E
Ponce
J
J
D000280:Administration, Inhalation; D000328:Adult; D001249:Asthma / Q000175:diagnosis / Q000503:physiopathology; D001985:Bronchial Provocation Tests; D002211:Capsaicin / Q000008:administration & dosage; D002908:Chronic Disease; D003371:Cough / Q000139:chemically induced / Q000209:etiology* / Q000503:physiopathology; D003937:Diagnosis, Differential; D004305:Dose-Response Relationship, Drug; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D005764:Gastroesophageal Reflux / Q000175:diagnosis / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009668:Nose Diseases / Q000175:diagnosis / Q000503:physiopathology; D011446:Prospective Studies; D012018:Reflex / Q000187:drug effects* / Q000502:physiology; D015203:Reproducibility of Results; D013577:Syndrome
D002211:Capsaicin