A proposal for the application and scoring of the Clock Drawing Test in Alzheimer's disease

Introduction. The Clock Drawing Test (CDT) has been wed in recent years as a simple neuropsychological instrument to assess cognitive deterioration associated with dementia, even though uniform operative criteria with respect to its application and scoring have not been established. Objective. To present application normatives and establish the most relevant psychometric criteria of the CDT in a sample of healthy subjects (HS) and patients with Alzheimer's disease (AD). Patients and methods. 56 patients were selected of which 35 were female and 21 were male. The patients' mean age was 72.7 with a standard deviation of 7.64. All of whom where probable AD patients according to the NINCDS-ADRDA criteria at stage 1 CDR. The group of HS was made up of 56 control subjects (34 female, 22 male) with a mean age of 72.14 and a standard deviation of 7.2. The CDT was applied in both its command (COM ) and copy (COP) experimental conditions. Results. The main psychometric parameters analysed in the studied series showed the following values: internal consistency (Cronbach's alpha coefficient 0.9029); cut off point CT COM 6 with 92.80, sensitivity; false negatives (FN) 72 with a specificity rating 93.48; false positive (FP) 6.52 with 93.16 efficacy; cut off point CT COP 8 with 73. 1 I sensitivity; FN 26.89 with 90.58 specificity, FP 9.42 with 82.49 efficacy. Conclusion. The CDT can be used to discriminate between HS and those in the initial stages of AD in the given sample rising the established application and scoring criteria.