30-day Spirometry Holter method design and prospective observational study.

Asthma underdiagnosis and overdiagnosis remain significant problems for healthcare systems worldwide and indicate considerable pain points with current guidelines and diagnostic methods; therefore, new, targeted approaches seem crucial. This study introduces a novel spirometry-based approach using digital tools for objective asthma diagnosis support. This was a single-centre (Warsaw Medical University, Poland) prospective cohort study. It included adults with suspected asthma per GINA 2020, without confirmed obstruction in ambulatory spirometry. Patients were equipped and trained with a portable spirometer with built-in manoeuvre quality features AioCare® (HealthUp, Poland). The protocol included twice-daily spirometry examinations over four weeks and symptom reporting in the mobile app. The number of obstructions detected, probability of finding obstruction over time, spirometry values' variability, technical correctness, and reported symptoms were evaluated. 26 patients enrolled (14 females, mean age 37.6 years old, BMI 24.7 kg/m^2), with a primary outcome of observed obstruction in 42% of participants (3.08 per patient, 95%CI: 0.78-5.37). The detection probability of obstruction plateaued at 100% within the first 21 days of monitoring. Diurnal PEF and FEV1 variability were exceeded (≥ 10%) in 73% and 66% of patients, respectively. 88% of participants performed over half of their tests correctly. 85% of patients reported symptoms at least once. The Spirometry Holter is a novel and feasible tool for monitoring airway limitation variability in line with GINA guidelines. It shows promise in objectively supporting asthma diagnoses in treatment-naive patients lacking documented prior obstruction.