[Rapid Disability Rating Scale-2 in Alzheimer's disease: NORMACODEM project data].

INTRODUCTION:The study aimed to investigate the Rapid Disability Rating Scale-2 (RDRS-2) in Alzheimer's disease (AD). Test retest reliability, internal consistency, data of discriminant validity of the scale, correlations with other functional and cognitive measures were analyzed. MATERIAL AND METHODS:451 subjects were assessed: 254 healthy controls, 86 with cognitive impairment but no dementia (CIND) and 111 subjects diagnosed of AD. Total and subscales scores of the RDRS-2 were obtained. The total score is the sum of three subscales: activities of daily living, disability, and special problems. To establish its correlation with other functional scales and cognitive instruments, the following tools were applied: Blessed Dementia Rating Scale (BDRS), Interview for the Deterioration of Daily Living in Dementia (IDDD), Alzheimer's Disease Assessment Scale-Cognitive (ADAS-Cog) and the Mini-Mental State Examination (MMSE). STATISTICAL ANALYSIS:lineal multivariate regression analysis. Crossvalidation. ROC curves. Intraclass coefficient. Cronbach's alpha and Pearson's Correlation coefficient. RESULTS:RDRS-2 scores by group were the following (mean and SD): Controls (18.95; 1.64), CIND (20.61; 2.88), and AD (28.96; 9.07). Results from regression analysis 282 demonstrated absence of influence of sociocultural variables such as age and education in RDRS-2 scores. Correlations with other instruments were as following: BDRS, r=0.820; IDDD, r=0.882; ADAS-Cog, r=0.762, and MMSE, r=0.742. Intraclass coefficient was 0.86 and Cronbach's alpha was 0.91. For the RDRS-2 the best cutoff score was 21 (82.88% sensitivity and 88.8% specificity). Area under the ROC curve was 0.92. CONCLUSIONS:The Spanish adaptation of the RDRS-2 is free of sociocultural influence, and shows very adequate data on internal consistency and stability. Although not specifically designed for its use in AD it correlates highly and significantly with other functional scales as well as with the degree of cognitive impairment in AD.