The Clock Drawing Test
This is a screen for visuospatial, constructional praxis and frontal executive impairment that takes 1 or 2 minutes to complete. It is a simple bedside test that is independent of bias due to intellect, language or cultural factors. The clock drawing test does not detect early cognitive changes or discriminate between types of dementia raising questions about its suitability to be used in isolation.
There are a number of alternative ways of administering and scoring the CDT, such as those described by, Shulman (1993), Sunderland (1989) and Wolf-Klein (1989). Of these, the Shulman method has been found to be the most sensitive and specific screening test for mild-moderate dementia when used in conjunction with MMSE.
In the Shulman method, subjects are asked to add the numbers of a clock-face on to a pre-drawn circle and to mark in the hands to resemble a specified time. Results are scored as follows:
- a perfect clock
- mild visuospatial errors
- errors in denoting the specified time
- moderate visuospatial disorganisation
- severe visuospatial disorganisation
- no reasonable representation of a clock
It is a good idea to read the following article to familiarise yourself with each the commonly used CDT methods, as they are frequently used by doctors, allied health professionals and ACAT nurses.
Brodarty H and Moore C. 1997. The Clock Drawing Test For Dementia Of The Alzheimer’s Type: A Comparison Of Three Scoring Methods In A Memory Disorders Clinic. International Journal of Geriatric Psychiatry, 12: 619-627.
This brief validated screen (specifically for Primary Care) incorporates the Clock Drawing task. The test is available online.