Studies have shown the Clock Drawing Test (CDT) to be useful as a screening test between normal, elderly populations and those diagnosed with dementia. However, the results of studies which have looked at the utility of the CDT to help differentiate Alzheimer's dementia

(AD) and other dementias have been conflicting. The purpose of this study was to explore the utility of the CDT in discriminating between patients with AD and other dementias.

A review was conducted using MEDLINE, PsycINFO and Embase. Search terms included clock drawing or CLOX and dementia or Parkinson's Disease or Alzheimer's Disease or Dementia with Lewy Bodies (DLB) or Vascular Dementia (VaD) or Semantic Dementia.

20 studies were selected. In most of the studies included, no significant differences were found in CDT scores between AD and VaD, DLB, and Parkinson's disease dementia (PDD) patients. Frontotemporal dementia (FTD) patients consistently scored higher in the CDT than AD patients. Qualitative analyses of the type of errors seem to suggest a difference between AD and the other types of dementias.

Overall, the CDT score may be useful in distinguishing between AD and FTD patients, but shows limited value in differentiating between AD and VaD, DLB and PDD. Qualitative analysis of the type of CDT errors may be a useful adjunct in the differential diagnosis of the types of dementias.