Construct validity and reliability of scores on scales to measure the impairment of health-related quality of life in persons with asthma.

The purpose of this study was to test the reliability, validity, and effectiveness of a health-related quality of life (HRQOL) instrument--the MiniAQLQ--among persons with asthma who were using a web-based intervention for guided self-management (www.MyAsthma.com). The MiniAQLQ was completed online in 1999 by 307 participants referred to www.MyAsthma.com by their primary care physicians. Construct validity of the MiniAQLQ was assessed by principal components analysis; reliability was estimated using Cronbach's alpha coefficient; and differences in means between pretest and posttest were analyzed using paired t test. The analysis produced four empirically meaningful factors with reliability of scores ranging from 0.65 to 0.94. Participants reported significant improvement in HRQOL after participating in this intervention. The four factors (activities, symptoms, emotions, and environment) generated by the principal components analysis empirically supported the four domains used in the development of the MiniAQLQ. Scores for the four factors were internally consistent and assessed the distinct domains. The MiniAQLQ appears to be a psychometrically sound instrument for measuring HRQOL online among asthma patients who are participating in online interventions.