Validity of direct assessment of functional status as a tool for measuring Alzheimer's disease severity.

OBJECTIVE: to assess the validity of the Direct Assessment of Functional Status (DAFS) performance-based functional scale for the staging of dementia severity by comparing it with established clinical, functional and cognitive scales. PATIENTS AND METHODS: 93 consecutive Alzheimer's disease patients underwent DAFS. Socio-demographic variables, cognitive status (Mini-Mental State Examination; MMSE), global disease severity (Clinical Dementia Rating; CDR), disease duration, physical performance (Physical Performance Test, PPT) and functional status (as reported by the primary caregiver) were also recorded and basic (B) and instrumental (I) activities of daily living (ADL) assessed.
RESULTS: a significant correlation was found between DAFS and MMSE (Pearson's r = 0.60; P < 0.01), PPT (r = 0.54; P < 0.01) and CDR (Spearman correlation coefficient: -0.48; P < 0.01). A mild, significant correlation was found between DAFS score and daily function as reported by the primary caregiver (r = -0.30 for BADL and r = - 0.27 for IADL). On multiple regression analysis, only MMSE and PPT were independently associated with the DAFS score, explaining 56% of DAFS total variance. ADL scales did not independently contribute to DAFS variance. A multivariate regression model of the association of DAFS with CDR showed that the association was significant even after adjustment for MMSE and PET, suggesting that DAFS scores provide additional information on dementia severity.
CONCLUSION: DAFS is a valid tool for the assessment of dementia severity, capturing cognitive and physical aspects of disability.