Domiciliary diurnal variation of exhaled nitric oxide fraction for asthma control

A major goal of asthma management is maintaining optimal control. Current assessment is based on symptoms and lung function. We evaluated whether domiciliary daily home exhaled nitric oxide fraction ( F eNO) monitoring could be useful as an index of asthma control. 50 asthmatic subjects and 15 healthy volunteers with a range of asthma severity underwent asthma control questionnaire (ACQ), spirometry before and after salbutamol and sputum induction. F eNO and peak expiratory flow (PEF) were measured twice daily for 2 weeks. A record of exacerbations was obtained 3 months later. Diurnal F eNO variation in uncontrolled asthmatics was significantly greater than in controlled asthmatics (p<0.01). PEF variation was not different. The daily variation of F eNO levels was also greater in uncontrolled asthmatics compared with controlled asthmatic and healthy subjects (p<0.01). 80% of uncontrolled asthmatics experienced at least one or more exacerbations over the 3 months after the enrolment. The combination of diurnal F eNO variation ≥16.6% and ACQ scores ≥1.8 was best at predicting uncontrolled asthma (area under curve 0.91, 95% CI 0.86–0.97; p<0.001). Diurnal variation in F eNO can be used as a biomarker of asthma control and as a predictor of the risk of future exacerbation. Prospective studies are warranted. Diurnal variation in F eNO can be used as a biomarker of asthma control and a predictor of the risk of future exacerbation