Validity and Reliability of the Persian Version of the Disability Assessment for Dementia Scale

Background: As dementia progresses in the course of life, one’s functions may be reduced regarding to fulfill the activities of daily living. One of the most important factor to diagnose and determine the severity of dementia is to assess activities of daily living. Objectives: one the most important factor in determining the severity of dementia in the area of activities of daily living is disability assessment for dementia (DAD) scale, which is not available in Persian and there is no validity and reliability report for it in Iranian community. Therefore, the aim of this study was to provide a Persian version of the valid and reliable DAD scale to assess functional disability in patients with dementia of Alzheimer type within the scope of everyday living activities. Patients and Methods: After the permission from the developer of the original scale, we translated the English version to Persian according to the international quality of life assessment (IQOLA) approach. To review the clarity and the necessity of the items translated, content validity index (CVI) and content validity ratio (CVR) methods were applied. Also, to assess the reliability of the scale, test-retest and inter-rater reliability techniques were used. The internal consistency of the items was also measured using the Cronbach’s alpha coefficient. Results: Cronbach’s alpha coefficient was very good for the scale (Cronbach’s _ = 0.78) and the inter-rater reliability and test-retest reliability were excellent (intraclass correlation/ICC = 0.99, ICC = 0.99). The clarity and necessity of the translated items based on the scores of CVI and CVR were also acceptable. Conclusions: The Persian version of DAD, during the study, had a very good validity and reliability and can serve as a useful scale in clinical assessment of functional disability in patients with Alzheimer’s in the area of activities of daily living.