many studies sustained that the clock drawing test (CDT) was not able to accurately detect people with CDR = 0.5. Other researchers have promoted the use of scoring approaches with multiple scales that rate quantitative and qualitative features of the production. Nevertheless, these scoring systems are complex and time-consuming. We propose a new brief CDT' scoring system in order to find a good measure for mild cognitive decline which is at the same time easy to administer. we enrolled 719 subjects: n. 181 with mild Alzheimer's disease (AD); n. 200 with amnesic mild cognitive impairment (MCI) and n. 338 healthy elderly subjects (C). our CDT-three-cluster scoring system demonstrated a good sensitivity and an excellent specificity to discriminate MCI subjects from normal elderly (76 and 84 %, respectively) and an excellent sensitivity and specificity to discriminate patients affected by mild Alzheimer disease (CDR: 1) from normal elderly (91 and 90 %, respectively). We found that CDT' score = 1.30 discriminate people with MCI, whereas a score = 4.38 discriminate AD patients. The three-cluster-scoring-system demonstrated a good diagnostic accuracy, taking into account those error-items more predictive of cognitive decline: omission of numbers or hands, writing numbers or hands in a wrong position and writing numbers or hands in a different code. Our CDT' scoring system is very short and easy method which can be used also by non-specialist.
Keywords: clock drawing test; mild Alzheimer’s disease; mild cognitive impairment; scoring system.