Investigation of factors associated with difficult-to-control asthma.

Objective: To determine the prevalence of factors associated with difficult-to-control asthma.

Methods: Patients with severe asthma were selected from the outpatient asthma clinic of the Ribeirão Preto School of Medicine Hospital das Clínicas. The patients were divided into two groups: controlled severe asthma and difficult-to-control severe asthma.