Exhaled nitric oxide measurement is useful for the exclusion of nonasthmatic eosinophilic bronchitis in patients with chronic cough.
BACKGROUND
Nonasthmatic eosinophilic bronchitis (NAEB) is an important cause of chronic cough, and it can be diagnosed by an induced-sputum (IS) examination. However, an IS examination is a complex and time-consuming procedure, and it has limited clinical application. This study aimed to evaluate the role of exhaled nitric oxide (NO) for the investigation of chronic cough, especially of NAEB.


METHODS
Two hundred eleven nonsmoking patients with a cough lasting > 3 weeks were enrolled in the study. The patients were examined and investigated with conventional diagnostic tools, including an IS examination. Exhaled NO was measured by a chemoluminescent analyzer.


RESULTS
One hundred seventeen patients with adequate IS results were analyzed: asthma, n = 14; NAEB, n = 21; and "others," n = 82. Exhaled NO and IS eosinophils were significantly higher in the asthma group and NAEB group than in the others group. Exhaled NO and IS eosinophils were significantly correlated in the asthma and NAEB groups. In the nonasthmatic group, the sensitivity and specificity of exhaled NO for detecting NAEB, using 31.7 parts per billion as the exhaled NO cutoff point, were 86% and 76%, respectively. Positive and negative predictive values were 47% and 95%, respectively, and positive and negative likelihood ratios were 3.51 and 0.19, respectively.


CONCLUSIONS
We concluded that exhaled NO measurement may be useful as part of the initial evaluation for chronic cough, especially for the exclusion of NAEB. A low level of exhaled NO suggested little likelihood of NAEB for the nonasthmatic patients with chronic cough.
Oh
Mi-Jung
MJ
Department of Medicine, Bundang Jesaeng Hospital, Seongnam.
Lee
Jin-Young
JY
Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
Lee
Byung-Jae
BJ
Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
Choi
Dong-Chull
DC
Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea. Electronic address: dcchoi@skku.edu.
D000328:Adult; D000388:Air / Q000032:analysis*; D001944:Breath Tests / Q000379:methods; D029481:Bronchitis, Chronic / Q000150:complications / Q000175:diagnosis / Q000378:metabolism*; D003371:Cough / Q000175:diagnosis / Q000209:etiology / Q000378:metabolism*; D003937:Diagnosis, Differential; D004802:Eosinophilia / Q000150:complications / Q000175:diagnosis / Q000378:metabolism*; D045853:Exhalation / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000032:analysis*; D011446:Prospective Studies; D012680:Sensitivity and Specificity
D009569:Nitric Oxide