Performance of the Asthma Impact on Quality of Life Scale (A-IQOLS) in diverse asthma research populations and demographic sub-groups.

BACKGROUND: The Asthma Impact on Quality of Life Scale (A-IQOLS) assesses patient-perceived negative effect of asthma on quality of life (QoL). Its standard error of measurement is known, it has strong construct, convergent, and divergent validity, and provides information that is unique among asthma outcome measures.

OBJECTIVE: To characterize A-IQOLS' psychometric properties and suitability for use in demographically and clinically diverse adult asthma populations.

METHODS: Data from participants in five independent asthma studies, whose samples ranging from patients with well-controlled moderate asthma to patients with severe, poorly controlled asthma were pooled to determine the psychometric performance of A-IQOLS scores, overall and in multiple demographic, disease status, and study subgroups.

RESULTS: Pooled sample (n = 597) age averaged 45 years; 66% were female, 65% were White, 22% African American, 11% Hispanic, and 11% had ≤ high school education. The rated importance of its underlying life dimensions and the associations between A-IQOLS scores and lung function, symptoms, ACT, Juniper Mini-AQLQ, and Marks AQLQ scores was very similar regardless of patient demographic and clinical characteristics. A-IQOLS scores discriminated among the individual study samples as well as other patient-reported symptom and functional status measures. Distribution and anchor-based considerations suggest an A-IQOLS minimum clinically important difference (MID) in the vicinity of 0.50, and not smaller than 0.33, scale score units.

CONCLUSIONS: A-IQOLS is valid for research, and potentially clinical, use in demographically and clinically diverse patients.