Purpose The Airways Questionnaire 20 (AQ20) is a concise, disease-specific health-related quality of life (HRQL) measure applicable to a spectrum of obstructive respiratory conditions ranging from asthma to emphysema. We wished to assess the performance characteristics of the AQ20 using a modified instrument that accounts for the complete cessation of certain activities, evaluating its cross-sectional and longitudinal performance among various subtypes of airway disease.
Methods We revised 7 of the 20 original items of the AQ20 (AQ20-R) to allow for an additional response category for those unable to perform certain activities due to a respiratory condition. We tested the performance characteristics of the AQ20-R among 352 adults with COPD, asthma, or chronic bronchitis identified in a national random telephone sample. Concurrent validity of the AQ20-R was assessed in relation to physical health status (Short Form 12, Physical Component Score [SF-12 PCS]), lung function (FEV1 % predicted), and therapies used. Predictive validity was assessed by examining the longitudinal relationship between the AQ20-R and utilization of health care services reported at one year follow-up.
Results Twenty-one of 352 subjects responded as being unable to participate in at least one of seven activities queried. Compared with others, these subjects had higher AQ20-R scores (p≤0.01), indicating worse HRQL, and poorer physical health status as measured by the SF-12 PCS (p≤0.01). Mean AQ20-R scores differed significantly (ANOVA, p≤0.01) among the subjects with COPD (8.9, SD 5.2), asthma (6.7, SD 5.0) and chronic bronchitis alone (4.7, SD 4.2). Overall, the AQ20-R correlated moderately with the SF-12 PCS (r = –0.55, p≤0.01) and FEV1 (r = –0.43, p≤0.01), and was significantly associated (p≤0.01) with the use of each of the following: inhaled bronchodilators, inhaled corticosteroids, home nebulizer, oral corticosteroids, antibiotics, and home oxygen. Adjusting for respiratory condition and demographics, the AQ20-R was an independent predictor of follow-up outpatient visits (OR 2.2, 95% CI 1.6–3.1), emergency department visits (OR 2.9, 95% CI 1.9–4.6), hospitalization (OR 2.8, 95% CI 1.6–4.9), and admission to an ICU (OR 3.0, 95% CI 1.2–7.3).
Conclusions The revised AQ20 (AQ20-R) is a simple, disease-specific HRQL measure that takes into account activity limitation in those with the most severe disease. It is valid for use among various subtypes of obstructive airway disease.