Home-Based FeNO Monitoring with the Vivatmo me Device Reveals Type 2 Inflammatory Patterns of Patients with Asthma at Different Treatment Steps: The FeNO@Home Study

Abstract Introduction Fractional exhaled nitric oxide (FeNO) is an important type 2 (T2) asthma biomarker. Home-based FeNO monitoring can provide longitudinal data better reflecting the variable nature of T2 inflammation versus single-point data. We sought to compare longitudinal mean FeNO and variability (CV) in relation to asthma control, and to compare detection rate of T2FeNO inflammation at diagnostic (≥ 40 ppb in GINA 1) and on-treatment (≥ 25 ppb in GINA 2–5) cutoffs during home versus clinic measurements. Methods This was an observational study with once-daily home-based FeNO (Vivatmo me) and symptom diary in patients with asthma of different GINA steps performed over 3 months. Clinic FeNO, forced expiratory volume in 1 s (FEV1), and 5-item asthma control questionnaire (ACQ-5) scores were also collected at two visits (enrolment/study end). Results We enrolled 85 patients (n = 23 step 1, n = 37 steps 2–3, and n = 25 steps 4–5). Mean FeNO over 3 months was highest in uncontrolled steps 4–5 (p = 0.006), and FeNO variability in steps 2–3 (p = 0.046). Subjects with optimal control (ACQ < 0.75 both visits) had comparable mean FeNO values, but fewer patients with CV above the median vs. suboptimally controlled patients (39.1% vs. 54.1%; p = 0.03). In GINA 1, FeNO CV was lower in optimally controlled patients (p = 0.10). Mean FeNO was higher on symptomatic asthma days, particularly in step 1 (p = 0.002), with similar trends during loss of asthma control phases. Home FeNO increased the detection rate of T2FeNO inflammation at a diagnostic cutoff (≥ 40 ppb, step 1) from 8.7% (clinic FeNO) to 47.8% of subjects, and of on-treatment T2FeNO inflammation in GINA steps 2–3 and 4–5 from 58.3% to 83.3%, and 64% to 96%, respectively. Conclusion Home-based FeNO provides important information about airway inflammation, distinct and complementary to symptom control. Detection of T2FeNO inflammation is facilitated at all GINA steps at diagnostic and predictive/prognostic cutoffs, with important implications for management and diagnosis. Trial Registration German Clinical Trial Register (DRKS) DRKS00029118, registered July 1, 2022.