The Mini-Cog and its Use as an Alzheimer's Screening Test

Testing for Dementia with the Mini-Cog
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The Mini-Cog is a rapid screening test for Alzheimer's disease that takes only 3 to 5 minutes to administer. Unlike other popular Alzheimer's tests that measure several aspects of cognition, such as the MMSE and the MoCA, the Mini-Cog measures only two: short-term recall and clock drawing (person draws numbers and arms pointed at a specific time on a paper clock). Despite that, the Mini-Cog is extremely accurate at predicting whether someone has dementia.

As a screening test, however, it should not substitute for a complete diagnostic work-up.

Administration of the Mini-Cog

Administration of the Mini-Cog is very simple. First, the person is asked to repeat three unrelated words, which tests immediate recall. Then the person is asked to do the clock drawing test. The clock drawing test assesses multiple factors, but its ability to screen for executive functioning is especially helpful in identifying dementia. Finally, the person is asked to remember the three words, testing their memory after the distracting task of drawing the clock.

Scoring of the Mini-Cog

Scoring of the Mini-Cog is simple as well. A person is scored as having dementia if they recall none of the three words, or if they recall one or two of the three words and draw an abnormal clock. Similarly, a person is scored as not having dementia if they recall all three words or if they recall one or two of the three words but draw a normal clock.

Usefulness of the Mini-Cog

Unlike the MMSE, the diagnostic value of the Mini-Cog is not influenced by education level or language abilities. Sensitivity and specificity of the Mini-Cog, key properties of every screening test, are excellent. Sensitivity refers to the test's accuracy in identifying individuals with the disease (i.e., persons with Alzheimer's test as positive).

Specificity refers to the test's effectiveness in identifying people who do not have the disease (i.e., persons without the disease test as negative). 

Overall Advantages and Disadvantages of the Mini-Cog

The Mini-Cog's advantages are many: It is fast, simple, and superior even to the MMSE in predicting dementia. It has also been shown to be effective at identifying mild cognitive impairment, a condition that sometimes, but not always, progresses to Alzheimer's disease.

A disadvantage is that the scoring of the clock drawing test is vulnerable to different interpretations.

Sources:

Agrell B, Dehlin O. The clock-drawing test. Age and Ageing. 1998; 277: 399-403.

Borson S, Scanlan J, Brush M, et al.The Mini-Cog:'vital signs' measure for dementia screening in multi-lingual elderly.Int J Geriatr Psychiatry. 2000; 15: 1021-1027.

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