Fractional exhaled nitric oxide is a useful adjunctive modality for monitoring bronchial asthma

Abstract

Background and Objective: To evaluate the utility of fractional exhaled nitric oxide (FeNO) in monitoring asthma control. Materials and Methods: Steroid naïve nonsmoking asthmatics were recruited and followed for 6-8 weeks on standard treatment. Serial measurements of FeNO, peak expiratory flow rate (PEFR) variability, forced expiratory volume in 1 s (FEV1), bronchodilator reversibility (BDR), and asthma control test (ACT) score were measured at baseline and after 6-8 weeks of treatment. Results: One hundred and fifty-one patients were recruited over an 18-month period. These comprised 79 males (52.3%) with mean (standard deviation) age of 34.2 (11.6). Mean (SD) FeNO levels at baseline and after therapy were 45.4 (35.9) and 38.4 (23.7) ppb, respectively (P = 0.01). Baseline FeNO correlated strongly with FEV1 (r = -0.78, P < 0.001), ACT score (r = -0.76, P < 0.001), PEFR variability (r = -0.74, P < 0.001), and moderately with BDR (r = 0.50, P < 0.001). After treatment with inhaled steroids, the correlation remained strong with ACT score (r = -0.68, P < 0.001) but weakened with PEFR variability (r = -0.34, P = 0.01) and FEV1 (r = -0.36, P = 0.01). Conclusions: FeNO may be useful as an adjunctive noninvasive modality to assess asthma control in both steroid naïve asthmatics and asthmatics on treatment. However, the suboptimal sensitivity and specificity may limit its utility as a point-of-care single monitoring tool.