D2.171 - Clinical and demographic characteristics associated with a classification as difficult-to-treat asthma: data from the EPI-ASTHMA study

Difficult-to-treat asthma is defined by the Global Initiative for Asthma (GINA) based on the presence of uncontrolled asthma despite a high level of treatment.

Aims: 1) To estimate the prevalence of difficult-to-treat asthma in adults with asthma in Portugal, and 2) to describe clinical and demographic characteristics associated with a classification as difficult-to-treat asthma.

The EPI-ASTHMA observational study used a 4-stage strategy to recruit (S0), screen (S1), characterize (S2), and follow up (S3) adults (≥18 years old) with asthma. Participants were randomly selected from 38 primary care units in mainland Portugal. Classification as difficult-to-treat asthma was based on GINA recommendations, using data from stage S2. High treatment level was considered when at GINA treatment step 4-5 and uncontrolled asthma in the presence of current poor symptom control (CARAT ≤24) or recent moderate-severe exacerbations (≥2 with systemic corticosteroids or ≥1 with hospitalization, in the last year). Prevalences were weighted for the Portuguese population.

The prevalence of difficult-to-treat asthma was 12.4[9.8-15.6]% (population estimate: 55.6 [43.1-68.1] thousand individuals). The prevalence was significantly higher in individuals aged ≥65 years, retired, female, with a family history of asthma, longer disease duration, at least two associated comorbidities, and FEV1 below the lower limit of normal (LLN; Table 1). When adjusted for sex and age group, the odds ratio (OR) for difficult-to-treat asthma remained significantly higher in the retired (OR 4.10[1.48-11.38]) and in those with asthma symptoms for >20 years (OR 2.35[1.20-4.62] if 20-40 years and 2.32[1.13-4.79] if >40 years).

The prevalence of difficult-to-treat asthma in Portuguese adults is in line with those described in other countries. Longer asthma duration and being retired were independently associated with classification as difficult-to-treat asthma.