Measuring disease-specific quality of life in obstructive airway disease: validation of a modified version of the airways questionnaire 20.

Background: The Airways Questionnaire 20 (AQ20) is a concise measure of health-related quality of life (HRQL) in obstructive airway disease; however, its original format may underestimate impairment due to the complete cessation of certain activities.
Methods: We revised seven items of the original AQ20 (revised AQ20 [AQ20-R]), adding response options for inability to perform certain activities. We assessed the performance of the AQ20-R among 352 adults with various airway conditions identified through a random telephone sample. Concurrent validity of the AQ20-R was assessed relative to the Short Form-12 (SF-12) physical component summary (PCS), FEV(1), and medication use. Predictive validity was assessed relative to health-care utilization among 278 subjects studied longitudinally.
Results: Twenty-one of 352 subjects were unable to perform at least one activity. These subjects demonstrated higher AQ20-R scores (p < 0.001) indicating worse HRQL. Mean (+/- SD) AQ20-R scores differed significantly (p < 0.001) among subjects with COPD (8.9 +/- 5.2), asthma (6.7 +/- 5.0), and chronic bronchitis (4.7 +/- 4.2). At baseline, the AQ20-R correlated with the SF-12 PCS (r = - 0.55, p < 0.001) and FEV(1) (r = - 0.43, p < 0.001), and was associated with the use of respiratory-specific therapies (p </= 0.001). In multivariate models, the AQ20-R was an independent predictor of outpatient visits (odds ratio, 2.2; 95% confidence interval, 1.6 to 3.1), emergency department visits (odds ratio, 2.9; 95% confidence interval, 1.9 to 4.6), hospitalization (odds ratio, 2.8; 95% confidence interval, 1.6 to 4.9), and ICU admission (odds ratio, 3.0; 95% confidence interval, 1.2 to 7.3) during the following year.
Conclusions: The AQ20-R is a valid respiratory-specific HRQL measure that accounts for activity cessation among the most impaired and can be used across various airway conditions.