DAD-6: an abbreviated version of the DAD scale (disability assessment for dementia) An instrument for detection of loss of autonomy at an early stage

This paper presents the French version of DAD-6, a validated instrument for the assessment of IADL (instrumental activities of daily living) considered as intentional and complex activities. A loss of autonomy remains a major criterion in the diagnosis of dementia. In addition, IADL assessment is recommended as a primary outcome in dementia drug trials. Since the publication in 1969 by Lawton and Brody of an IADL scale, many instruments have been developed. However, their psychometric properties remain to be improved. The need for improving the early diagnosis yielded to the design of DAD-6, an instrument allowing capturing subtle difficulties in IADL management. The DAD-6 scale emphasizes the role of the cognitive function, mainly the executive function in early IADL impairment. DAD-6 requires the participation of an informant (a patient's proxy). Relative to patients' self-reports or performance-based methods, informant-based questionnaires are the most common and practical methods used in memory clinics. In previous work, DAD-6 score gradually decreased with increasing severity of the cognitive status. The present work shows the inter-rater reliability of DAD-6. The use of the scale with the same informants by one neurologist and two neuropsychologists, separately, indicated a high agreement between raters (alpha of Krippendorff > 0.80). This work also highlights the main sources of bias in the context of evaluation based on subjective judgement. The authors stress the necessity of: 1 - a clarification of the relationship between cognitive function and IADL; 2 - the measurement of IADL performance in a routine neuropsychological assessment by experienced professionals.