The International Classification of Functioning, Disability and Health-orientated Occupational Therapy Assessment: a Rasch analysis of its domains

The aim of the study was to evaluate and improve the psychometric properties of the Occupational Therapy Assessment (OTA) by means of Rasch analysis. The OTA is a tool developed to enhance diagnostics, documentation, therapy planning and evaluation of the individual client process in occupational therapy for adult clients. To assess the central aspects concerning patients' activities and the consequences of their impairments on these activities, therapists rated 50 items relating to the five domains 'activities for self-care, 'activities for independent living, 'consequences of sensory-motor functions in everyday life, 'consequences of neuropsychological functions in everyday life' and 'consequences of psychosocial functions in everyday life'. The study sample consisted of 785 patients consecutively admitted to 44 institutions. These patients participated in occupational therapy and suffered from functional, neurological, psychiatric or multiple impairments (geriatrics). For each OTA domain, unidimensional item groups could be identified. Psychometric properties were satisfactory in all medical fields except for psychiatric patients. Between different medical fields, for all domains, differential item functioning exists, indicating field-specific definitions of the latent dimensions. The OTA provides a psychometrically well developed and tested basis for diagnostic and evaluative purposes in occupational therapy settings.