Objective: To evaluate whether the Portuguese version of the Asthma Control Questionnaire (ACQ) is a valid instrument to measure asthma control in adult outpatients in Brazil.
Methods: We selected 278 outpatients diagnosed with asthma. All of the patients completed the questionnaire, underwent spirometry and were clinically evaluated by a physician in order to characterize the control of the disease in the first visit. The questionnaire was evaluated in three versions, with 5, 6 and 7 questions, respectively, and scores of 0.75 and 1.50 were used as cut-off points.
Results: Of the 278 patients, 77 (27.7%) had intermittent asthma, 39 (14.0%) had mild persistent asthma, 40 (14.4%) had moderate persistent asthma and 122 (43.9%) had severe persistent asthma. The sensitivity of ACQ to identify uncontrolled asthma ranged from 77% to 99%, and the specificity ranged from 36% to 84%. The positive predictive value ranged from 73% to 90%, and the negative predictive value ranged from 67% to 95%. The positive likelihood ratio ranged from 1.55 to 4.81, and the negative likelihood ratio ranged from 0.03 to 0.27. In the 5- and 6-question versions of the ACQ, the intraclass correlation coefficient was 0.92. These two versions were both responsive to clinical changes in the patients.
Conclusions: All three versions of the ACQ satisfactorily discriminated between patients with uncontrolled asthma and those with controlled asthma. The 5- and 6-question versions also presented good reliability and responsiveness. Therefore, the ACQ is a valid tool for evaluating asthma control in adult outpatients in Brazil.