Comparative analysis of two quality-of-life instruments for patients with chronic obstructive pulmonary disease

The St. George's Respiratory Questionnaire (SGRQ) has been validated and widely used in assessing quality of life among patients with chronic obstructive pulmonary disease (COPD), but it is time-consuming and complicated to score. A more concise instrument, the Airways Questionnaire (AQ), was developed to measure quality of life (QoL) among patients with asthma and COPD. The shorter version of this instrument has 20 items (AQ20) and the longer version has 30 items (AQ30). The purpose of this study was to determine the relationship between QoL scores measured by the AQ20/30 or the SGRQ scale and utilization of health-care services by COPD patients and to evaluate the comparative advantage of any one of these instruments in measuring the QoL of COPD patients.

Results from a survey of 1000 patients participating in a pilot COPD health management program were used for this analysis. A total of 303 patients completed both the AQ20/30 and the SGRQ questionnaires. Logistic regression models were used to analyze the relationship between utilization of health care services and QoL scores while controlling for a set of covariates. Spearman's rank correlation was used to determine whether the AQ30 and the SGRQ scores for symptoms, activity, and impact, and the overall scores were correlated.

The regression results demonstrate that there is a strong relationship between quality-of-life scores and health-care utilization variables. Moreover, the degree of association between the AQ20/30 scores and utilization variables and the SGRQ and utilization variables are comparable. Both the AQ20 and the AQ30 were highly correlated with the overall SGRQ score and with symptoms, activity, and impact component scores.

The AQ20/30 and the SGRQ scores are comparable in terms of measuring QoL in COPD patients and are equally useful in determining the association between utilization of health-care services and QoL.