The Clock-Drawing Test (CDT) has been used to screen for Alzheimer's disease (AD) as a supplement to cognitive tests that focus on memory impairment. We examined a comprehensive scoring system of the CDT in screening of AD in a Chinese population and derived a simplified scoring system. All 403 (144 AD and 259 nondemented) subjects were administered the CDT, including both the drawing part (CDT-D) and the copying part (CDT-C). The Cognitive Abilities Screening Instrument and the Clinical Dementia Rating were also administered. Stepwise discriminant analysis was used to develop a simplified CDT scoring system. The optimal CDT cutoff scores (CDT-D: 10/11; CDT-C: 12/13) show intermediate sensitivity (CDT-D: 66.7%; CDT-C: 51.4%) and specificity (CDT-D: 74.5%; CDT-C: 74.1%). The simplified 3-item CDT scoring system, with a cutoff score of 2/3, has a sensitivity of 72.9% and a specificity of 65.6%; it can be used as a quick test for AD screening.
