Background: The Rasch model prescribes procedures to ensure that a scale constructed from multiple items conforms to fundamental requirements of interval scales of measurement.
Objective: To test the Rasch properties of the domains of the World Health Organization Quality of Life Instrument-abbreviated version (WHOQOL-BREF) in depressed patients from primary care settings.
Design: Cross-sectional, cross-national study.
Setting: Primary care.
Patients: The sample consisted of 1193 patients having a confirmed diagnosis of depression from 6 countries (Australia, Brazil, Israel, Russia, Spain, and the United States) involved in the Longitudinal Investigation of Depression Outcomes (LIDO) study.
Measurements: The Composite International Diagnostic Interview (CIDI) diagnosed depression, whereas the Center for Epidemiological Studies Depression Scale (CES-D) assessed severity of depression. The WHOQOL-BREF measured generic quality of life (QOL).
Results: Three of the 4 WHOQOL-BREF domains (physical, psychological, and environment) conform to the Rasch model expectations, following adjustments required mainly because of individual item misfit or differential item functioning (DIF) due to age or country. The social domain showed relatively poor psychometric properties, as observed in previous studies.
Conclusions: The Rasch analysis demonstrated that, with some modifications, all domains of the WHOQOL-BREF, except for the social domain, provide an interval scale measure of generic subjective QOL in the context of depressed primary care patients in 6 countries worldwide.