Development and validation of the Asthma Life Impact Scale (ALIS).

BACKGROUND

Current asthma patient-reported outcome (PRO) measures focus on symptoms and functioning and may not capture the holistic impact of asthma on the quality of life of the patient.

OBJECTIVE

To develop a PRO measure capturing the overall impact of asthma on patient's quality of life.

METHODS

Items for the Asthma Life Impact Scale (ALIS) were generated from patients with asthma during interviews in the UK and focus groups in the US. The ALIS was tested with UK and US asthma patients during cognitive debriefing interviews and included in large, two-administration, validation studies in the UK and US.

RESULTS

Issues raised by asthma patients during interviews (n = 39 patients) and focus groups (n = 16 patients) were included in the draft ALIS. Cognitive debriefing interviews with 29 UK and US asthma patients showed that the scale was relevant and comprehensive. 140 UK and 185 US asthma patients participated in the validation study. The analysis showed that the ALIS measures a single construct, namely the overall impact of asthma on patients' quality of life. Internal consistency (Cronbach's Alpha) was high (UK = 0.94; US = 0.92) as was test-retest reliability (UK = 0.93; US = 0.83). Patients reporting worse general health or more severe asthma had significantly higher ALIS scores (p < 0.001) (indicating greater negative impact of asthma). Correlations with the Asthma Quality of Life Questionnaire were moderate to high.

CONCLUSIONS

The final 22-item ALIS is unidimensional, reliable and valid, and a valuable tool for comprehensively assessing the holistic impact of asthma from the patient's perspective.