The Fractional Exhaled Nitric Oxide and Serum High Sensitivity C-Reactive Protein Levels in Cough Variant Asthma and Typical Bronchial Asthma

Fractional exhaled nitric oxide (FeNO) is known to be a good marker of airway eosinophilic inflammation in bronchial asthma. Recently, serum high sensitivity C-reactive protein (hs-CRP) has been shown to be also useful to detect the airway inflammation. Newly diagnosed 90 cough variant asthma and 92 bronchial asthma patients were enrolled. FeNO, serum hs-CRP, pulmonary function tests, bronchial hyperresponsiveness, IgE and sputum eosinophils ratio were compared. Ninety healthy control subjects were set for FeNO and serum hs-CRP normal range reference. We have compared the clinical utilities of FeNO and serum hs-CRP to differentiate bronchial asthma and cough variant asthma. FeNO was significantly higher in bronchial asthma (92.6 ± 85.5 ppb) than in cough variant asthma (35.6 ± 43.3; p < 0.001) and both were significantly higher than normal range (18.0 ± 6.4, p < 0.001, respectively), and in differentiating between the two groups showed a sensitivity of 0.69 and a specificity of 0.73 at the cutoff value of 28 ppb. Serum hs-CRP did not differ significantly between bronchial asthma (723 ± 1162 ng/ml) and cough variant asthma (558 ± 758) even if both were significantly higher than normal range (345 ± 401, p < 0.01 and p < 0.05 respectively). FeNO is more useful than serum hs-CRP in differentiating patients with bronchial asthma from those with cough variant asthma, and healthy persons.