Internal consistency & validity of Indian Disability Evaluation and Assessment Scale (IDEAS) in patients with schizophrenia

BACKGROUND & OBJECTIVES: The Indian Disability Evaluation and Assessment Scale (IDEAS) has been recommended for assessment and certification of disability by the Government of India (GOI). However, the psychometric properties of IDEAS as adopted by GOI remain understudied. Our aim, thus, was to study the internal consistency and validity of IDEAS in patients with schizophrenia. METHODS: A total of 103 consenting patients with residual schizophrenia were assessed for disability, quality of life (QOL) and psychopathology using the IDEAS, WHO QOL-100 and Positive and Negative symptom scale (PANSS) respectively. Internal consistency was calculated using Cronbach's alpha. For construct validity, relations between IDEAS, and psychopathology and QOL were studied. RESULTS: The inter-item correlations for IDEAS were significant with a Cronbach's alpha of 0.721. All item scores other than score on communication and understanding; total and global IDEAS scores correlated significantly with the positive, negative and general sub-scales, and total PANSS scores. Communication and understanding was significantly related to negative sub-scale score only. Total and global disability scores correlated negatively with all the domains of WHOQOL-100 (P<0.01). The individual IDEAS item scores correlated negatively with various WHOQOL-100 domains (P< 0.01). INTERPRETATION & CONCLUSIONS: This study findings showed that the GOI-modified IDEAS had good internal consistency and construct validity as tested in patients with residual schizophrenia. Similar studies need to be done with other groups of patients.