To assess the feasibility of the procedures of EPI-ASTHMA. EPI-ASTHMA is a population-based multicentre stepwise study about the prevalence and characterisation of patients with asthma based on disease severity in Portugal. Methods: A pilot study of EPI-ASTHMA was conducted with adults from three primary care centres. We followed a stepwise approach comprising 4 stages: stage 0-invitation phone call (n ~1316); stage 1-telephone interview (n ~658); stage 2-clinical assessment with physical

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... ation, diagnostic tests, and patient-reported outcome measures, to confirm the diagnosis of those with possible asthma at stage 1 (n ~160); stage 3-characterization of a subgroup of asthma patients by collecting data through a telephone interview, patient file review and CARATm app (n ~40), after 3-months. The frequency of asthma was calculated in relation to the entire study population (stage 1) and the frequency of difficult-to-treat/severe asthma in relation to the number of asthma patients (stage 3). Results: From 1305 adults invited, 892 (68%) accepted to participate (stage 0) and 574 (64%; 53[42-67] y; 43% male) were interviewed (stage 1). From those, 148 (26%; 60[46-68] y; 43% male) were assessed at stage 2, and 46 (31%; 51[39-67] y; 44% male) were diagnosed with asthma. Half of these patients (n = 23) accepted to install the app. Stage 3 was completed by 41 (93%) patients, of whom 31 (83%) had asthma confirmed by their file review. A total of 8% of participants had asthma, of those 17% had difficult-to-treat and 5% severe asthma. Conclusion: Attained recruitment rates and the quality of the results confirmed the feasibility of the EPI-ASTHMA stepwise approach. This pilot study provided insight into the improvement of the procedures to be generalized across the country.