Developing an item bank to measure economic quality of life for individuals with disabilities

Objective: To develop and evaluate the psychometric properties of an item set measuring economic quality of life (QOL) for use by individuals with disabilities.

Design: Survey.

Setting: Community settings.

Participants: Individuals with disabilities completed individual interviews (n=64), participated in focus groups (n=172), and completed cognitive interviews (n=15). Inclusion criteria included the following: traumatic brain injury, spinal cord injury, or stroke; age ≥18 years; and ability to read and speak English. We calibrated the items with 305 former rehabilitation inpatients.

Interventions: None.

Main outcome measure: Economic QOL.

Results: Confirmatory factor analysis showed acceptable fit indices (comparative fit index=.939, root mean square error of approximation=.089) for the 37 items. However, 3 items demonstrated local item dependence. Dropping 9 items improved fit and obviated local dependence. Rasch analysis of the remaining 28 items yielded a person reliability of .92, suggesting that these items discriminate about 4 economic QOL levels.

Conclusions: We developed a 28-item bank that measures economic aspects of QOL. Preliminary confirmatory factor analysis and Rasch analysis results support the psychometric properties of this new measure. It fills a gap in health-related QOL measurement by describing the economic barriers and facilitators of community participation. Future development will make the item bank available as a computer adaptive test.