Domiciliary Fractional Exhaled Nitric Oxide and Spirometry in Monitoring Asthma Control and Exacerbations.

BACKGROUND:Domiciliary measurements of airflow obstruction and inflammation may assist healthcare teams and patients in determining asthma control and facilitate self-management. OBJECTIVE:To evaluate parameters derived from domiciliary spirometry and fractional exhaled nitric oxide (Feno) in monitoring asthma exacerbations and control. METHODS:Patients with asthma were provided with hand-held spirometry and Feno devices in addition to their usual asthma care. Patients were instructed to perform twice-daily measurements for 1 month. Daily symptoms and medication change were reported through a mobile health system. The Asthma Control Questionnaire was completed at the end of the monitoring period. RESULTS:One hundred patients had spirometry, of which 60 were given additional Feno devices. Compliance rates for twice-daily measurements were poor (median [interquartile range], 43% [25%-62%] for spirometry; 30% [3%-48%] for Feno); at least 15% of patients took little or no spirometry measurements and 40% rarely measured Feno. The coefficient of variation (CV) values in FEV1 and Feno were higher, and the mean % personal best FEV1 lower in those who had major exacerbations compared with those without (P < .05). Feno CV and FEV1 CV were associated with asthma exacerbation during the monitoring period (area under the receiver-operating characteristic curve, 0.79 and 0.74, respectively). Higher Feno CV also predicted poorer asthma control (area under the receiver-operating characteristic curve, 0.71) at the end of the monitoring period. CONCLUSIONS:Compliance with domiciliary spirometry and Feno varied widely among patients even in the setting of a research study. However, despite significant missing data, Feno and FEV1 were associated with asthma exacerbations and control, making these measurements potentially clinically valuable if used.