Validity of the 36-item Persian (Farsi) version of the World Health Organization Disability Assessment Schedule (WHODAS) 2.0

The purpose of this study was to validate a self-administered 36-item Persian (Farsi) version of the World Health Organization (WHO) Disability Assessment Schedule II (now referred to as WHODAS 2.0) for assessment of psychiatric patients’ perceptions of their functioning and disability. WHODAS 2.0 items were analyzed using two approaches. Reliability, consistency, and factor structure were assessed using Cronbach’s α and factor analysis, and item response theory (IRT) was used to determine how well the WHODAS 2.0 items fitted the Rasch paradigm. Data were collected from 614 psychiatric outpatients in Tehran. The mean overall disability score for the sample was 37.57. The scale had excellent reliability (Cronbach’s α = 0.94). The IRT-based analysis showed that overall the set of items had a poor fit to the Rasch paradigm; the exceptions were items belonging to domains D1 (cognition), D2 (mobility), and D5 (life activities). There were several problematic items associated with dimensions D3 (self-care) and D4 (getting along). There were at least two badly fitted items associated with all dimensions. This study is the first to examine the psychometric properties of the self-administered, 36-item, Persian version of WHODAS 2.0 in psychiatric outpatients. This version has acceptable reliability and validity in psychiatric patients, but a reformulation of problematic items and further validation tests would be required to produce a robust measurement instrument.