D102-10 Self-Reported Adherence Substantially Overestimates Objectively Measured Inhaler Use: Findings From Kare Randomized Controlled Trial of a Digital Inhalation Coach in Asthma Patients

Abstract Rationale Treatment adherence is a key determinant of asthma control, yet its accurate assessment remains challenging. Conventional approaches such as patient self-reports are prone to recall and reporting bias. Digital inhalation tools enable objective monitoring of therapy use and technique, offering new insights into real-world adherence patterns. Using data from the KaRe study, we aimed to compare self-reported and objectively measured adherence in patients with asthma. Methods A multicenter, randomized, controlled study (KaRe) was conducted at 15 German sites. Adults with asthma (≥18 years) were assigned 1:1 to 12 weeks of the KATA Inhalation App or a control app after a 1-week baseline phase. The study was open-label for subjects and investigators, but inhalation recordings were centrally and blindly evaluated. Adherence was assessed both subjectively using the Test of Adherence to Inhalers (TAI) and objectively from the inhalation videos. TAI consists of ten questions filled out by patients and two by physicians. Results A total of 147 patients across all levels of asthma severity (27.3 % mild, 48.9 % moderate, 23 % severe) were included. The ITT analysis population (N = 139) covered wide age range from 19 to 87 years (mean 53 ± 16; 65.5 % male, 34.5 % female). Main inhaler types included dry-powder inhalers (DPI, 48.9 %), pressurized metered-dose inhalers (pMDI, 44.6 %) and soft-mist inhalers (SMI, 6.5 %), with 88.5 % of patients on multi-inhaler therapy. Based on TAI scores, self-reported adherence was good in 37.9 %, moderate in 35.6 %, and poor in 26.5 % of patients at baseline, with no significant changes or between-group TAI differences observed at study completion (difference = 0, p = 0.887). The objective adherence was similar in both groups, with 14% missed inhalations at study end. Notably, physicians tended to overestimate patient adherence, as indicated by high physician-rated TAI scores (97% no severe errors) despite persistently high error rates in video assessments (1,4 errors/inhalation on baseline) and a subsequent improvement in the intervention group relative to control at study end (IRR 0.42; p 0.001). Conclusion Self-reported adherence substantially overestimated objectively measured inhaler use, highlighting the limitations of questionnaire-based assessment. Digital inhalation monitoring offered a more accurate and nuanced understanding of real-world adherence by capturing both medication use and inhalation technique, thereby supporting its integration into routine asthma management. This abstract is funded by: VisionHealth GmbH