Validity of the Portuguese version of Clinical Dementia Rating

Objective To evaluate the validity of the Portuguese version of the Clinical Dementia Rating for classifying the cognitive function among the elderly. Methods The Mini Mental State Examination was utilized as a screening method for cognitive deficit among a cohort of 424 elderly. All those who scored < 26 points (108 elderly) and 48 elderly with scores 226 were included in the study. The 156 subjects selected were submitted to clinical evaluation and neuropsychological tests for the diagnosis of dementia. Afterwards, both cases and non-cases were classified, according to the Portuguese version of the Clinical Dementia Rating, in the categories normal, borderline, mild, moderate and severe dementia. Results Among the 156 subjects selected, 122 were non-cases, 62 (51%) were classified as normal (CDR=0) and 60 (49%) as borderline (CDR=0.5). Among the 34 cases of dementia, 17 (50%) were classified as mild dementia (CDR = 1), eight (23%) as moderate (CDR = 2) and six (18%) as severe dementia (CDR = 3). Only three (9%) of the cases were considered borderline cases by the Clinical Dementia Rating. Its sensibility was 91.2% and the specificity was 100%. The positive predictive value was 100% and the negative predictive value was 97.6%. The Mini Mental State Examination scores declined significantly according to the degree of dementia. Conclusions The Portuguese version of the Clinical Dementia Rating is a valid instrument for classifying the dementia status of the elderly. Almost half the cases considered normal by the diagnostic criteria of the Mini Mental State Examination were borderline cases according to the Clinical Dementia Rating and might correspond to cases of mild cognitive impairment, with an increased risk of conversion to dementia cases.