Validation and psychometric properties of the Asthma Control Questionnaire among children

Background The Asthma Control Questionnaire (ACQ) is a patient-centered tool for evaluating asthma control. It has been validated in adults, but not well-validated among children. Objective We evaluated the reliability, validity, and responsiveness to change of the ACQ for assessing asthma control in children ages 6 to 17 years. A threshold value for poor disease control and a minimally important difference were also determined. Methods Data from 305 asthmatic children enrolled in a clinical trial were examined. The ACQ was administered at 8 visits. We analyzed results for the combined age group and for the 6- to 11-year-old and 12- to 17-year-old age groups separately. Results Overall, the Cronbach α value (internal consistency) for the ACQ was 0.74 at baseline, and the intraclass correlation coefficient (test-retest reliability) for repeated questionnaires among stable patients was 0.53. The Pearson correlations between the ACQ and other asthma questionnaires were moderate to strong (-0.64 to -0.73). Mean ACQ scores were higher (worse) in patients whose peak flow decreased, who used more rescue medications, or who sought medical care for asthma than in patients who were stable (P <.0001 for all measures). Changes in ACQ scores were significantly different among patients with deteriorating, improving, or stable asthma symptoms (P ≤.01). The optimal threshold indicating poor asthma control was 1.25 or greater. The minimally important difference was established to be 0.40. Results for the separate age groups were similar. Conclusion The ACQ is a moderately reliable, valid, and responsive tool with adequate psychometric properties for assessing recent asthma control among children.