Introduction Domiciliary measurements of airflow obstruction and inflammation may assist healthcare teams and patients in determining asthma control and facilitate self-management. We report on the analysis of the physiological and behavioural data of domiciliary use of spirometry and fractional exhaled nitric oxide (FeNO) in patients with asthma. We investigated the compliance rate with these measurements, and explored which parameters were predictive of disease-related outcomes during and after the monitoring period.
Method We used data collected from the EU-Horizon 2020 myAirCoach study, which utilised an app-based platform to facilitate data collection. Patients were provided with hand-held spirometry and FeNO devices in addition to their usual asthma care, and instructed to perform twice-daily measurements for one month. Daily symptoms and medication change were reported through the mobile health system. The Asthma Control Questionnaire was completed at the end of the monitoring period.
Results One hundred patients were provided with home-spirometry equipment, and 60 of these were also given FeNO devices. Compliance rates for twice-daily measurements were low (median [IQR]: 43 (25–62)% for spirometry; 30 [3–48]% for FeNO); 15% of patients rarely took measurements for spirometry and 40% for FeNO (defined as ≤7 data points over a month). The compliance rate was not associated with patient factors such as gender, internet-experience, education or general health. Despite the heterogeneity of compliance rate and missing data, the coefficient of variation (CV) in FEV1 and FeNO were higher, and the mean% personal best FEV1 lower in those who had major exacerbations during monitoring period compared to those without (p<0.05) (figure 1). FeNO CV and FEV1 CV were associated with asthma exacerbation during the monitoring period (AUROCC: 0.79 and 0.74, respectively) and FeNO CV was predictive of poor asthma control (AUROCC: 0.71) at the end of the monitoring period.
Conclusion Compliance with domiciliary spirometry and FeNO varied widely amongst patients even in the setting of a research study. However, despite significant missing data, FeNO and FEV1 predicted asthma exacerbations and control during and following monitoring periods, making these measurements potentially clinically valuable if used.
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