Comparing clock tests for dementia screening: naïve judgments vs formal systems--what is optimal?

Area of Science:

• Neurology
• Geriatrics
• Cognitive Assessment

Background:

• Clock drawing tests (CDTs) are used for dementia screening but vary in format, scoring, and complexity.
• This study compared the dementia screening performance of seven CDT scoring systems and untrained raters.

Purpose of the Study:

• To evaluate and compare the diagnostic accuracy of different Clock Drawing Test scoring systems.
• To assess the effectiveness of untrained raters in identifying dementia using CDTs.
• To determine if CDTs improve upon existing methods for dementia recognition, particularly for mild cases.

Main Methods:

• 80 clock drawings from subjects with known dementia status (normal, mild, moderate, severe) were analyzed.
• An expert scored clocks using seven established CDT scoring systems.
• 20 untrained raters judged clocks as normal or abnormal without formal scoring criteria.

Main Results:

• Formal CDT systems and untrained raters showed high agreement (90-100%) for normal, moderate, and severe dementia, but poor agreement for mild impairment (39%).
• The Mendez and CERAD systems demonstrated the highest accuracy in classifying dementia (84-85%).
• Untrained raters' judgments were as effective as five of the seven formal CDT systems.

Conclusions:

• The Mendez CDT system was the most accurate overall, though not significantly superior to the simpler CERAD system.
• Untrained raters demonstrated acceptable accuracy for community-based dementia screening.
• CDTs, particularly when used by physicians, can enhance the detection of mild dementia.