Abstract
BACKGROUND: The Asthma Impact on Quality of Life Scale (A-IQOLS) assesses the negative effect of asthma on quality of life (QoL) from the patient's perspective by using dimensions of Flanagan's Quality of Life Scale (QOLS), a measure of current QoL. OBJECTIVES: We sought to determine and compare the psychometric properties of the A-IQOLS and QOLS, including their sensitivities to differences and change in asthma status. METHODS: In a test-retest design (3- to 5-week interval) adults with persistent asthma underwent spirometry and were administered the A-IQOLS, other asthma outcome measures (Asthma Control Test, Asthma Symptom Utility Index, and the Marks and Juniper Asthma Quality of Life Questionnaires), and the QOLS. RESULTS: Participants' (n = 147) mean age was 49 years, 76% were white, 12% were Hispanic, and 65% were female. A-IQOLS and QOLS scores were significantly correlated with other asthma outcomes scores, except FEV(1), but shared relatively low common variance with these measures. A-IQOLS but not QOLS score changes were significantly correlated with changes in asthma outcomes. An A-IQOLS standard error of measurement of 0.27 implies that a within-person score change of ±0.73 or greater constitutes a true change. The QOLS standard error of measurement was 0.43. CONCLUSIONS: A-IQOLS provides a reliable, valid, and unique assessment of the patient-perceived negative effect of asthma on QoL that is suitable for use in asthma clinical research and potentially in clinical care. Further studies are needed in diverse patient populations. QOLS, a measure of current QoL, is less sensitive to disease status changes but might be useful in characterizing study populations, in treatment adherence research, and as a clinical and research tool in patients with multiple, severe, and/or life-limiting chronic conditions.