Exhaled nitric oxide levels in patients with atopic cough and cough variant asthma.
OBJECTIVE
Atopic cough (AC) is an established clinical entity in Japan, in which patients present with a chronic persistent non-productive cough. Exhaled nitric oxide (NO) is a biomarker of eosinophilic airway inflammation. The present study examined whether exhaled NO levels were increased in AC in comparison with cough variant asthma (CVA) and bronchial asthma (BA).


METHODS
Consecutive patients presenting with an isolated cough lasting at least 8 weeks were enrolled in the study. The aetiology of the chronic cough was determined according to the Japanese Respiratory Society guidelines for management of cough. Exhaled NO, capsaicin cough sensitivity (capsaicin concentration eliciting five or more coughs (C5)) and bronchial reversibility were measured at the patients' first visit. Bronchial responsiveness (PC20 to methacholine) was measured at their second visit following a 6-day course of bronchodilator therapy.


RESULTS
There were 58 patients recruited and fully investigated; of these 9 and 11 patients were diagnosed with AC and CVA, respectively, as single causes of chronic cough. Ten patients with BA who had not received corticosteroid therapy in the previous 4 weeks and who attended the same clinic in the same time period acted as controls. Exhaled NO levels in patients with AC were significantly lower than those in patients with CVA and BA. There was no significant difference in the exhaled NO levels between patients with CVA and BA.


CONCLUSIONS
Exhaled NO may reflect eosinophilic inflammation of peripheral airways and its measurement may be useful in differentiating CVA from AC and other causes of chronic non-productive cough.
Fujimura
Masaki
M
Respiratory Medicine, Cellular Transplantation Biology, Kanazawa University Graduate School of Medicine, Kanazawa, Japan. fujimura@med3.m.kanazawa-u.ac.jp
Ohkura
Noriyuki
N
Abo
Miki
M
Furusho
Shiho
S
Waseda
Yuko
Y
Ichikawa
Yukari
Y
Hara
Johsuke
J
D000328:Adult; D001249:Asthma / Q000175:diagnosis / Q000188:drug therapy / Q000378:metabolism*; D015415:Biomarkers / Q000378:metabolism; D001944:Breath Tests; D001985:Bronchial Provocation Tests; D001993:Bronchodilator Agents / Q000627:therapeutic use; D016022:Case-Control Studies; D003371:Cough / Q000175:diagnosis / Q000188:drug therapy / Q000378:metabolism*; D003430:Cross-Sectional Studies; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000378:metabolism*; D011014:Pneumonia / Q000378:metabolism; D012129:Respiratory Function Tests
D015415:Biomarkers; D001993:Bronchodilator Agents; D009569:Nitric Oxide