ACOVE recommends screening all vulnerable elderly patients who are new to a primary care practice or inpatient service, and following up with an annual evaluation to detect any changes in memory and function.18,19 Based on the recommendations of ACOVE and the USPSTF, all 3 patients described earlier would be candidates for screening.
Choosing the best screening tool
There is no serum or radiographic test available for the diagnosis of AD, and a thorough clinical evaluation can be extremely time-consuming. In the primary care setting, focused evaluations are both useful and cost effective.
There are a number of valid and reliable cognitive screening tools, including the Mini-Mental State Examination (MMSE), the Mini-Cog, the Montreal Cognitive Assessment (MoCA), the AD 8 Dementia Screening Interview, and the 7-Minute Neurocognitive Screen. In evaluating these and other screening tools, consider the sensitivity and specificity of each. Consider, too, features that may make one test better suited than another for a particular patient or specific circumstance (TABLE).
TABLE
Cognitive screening tools: How they compare
| TOOL (TIME TO ADMINISTER) | ADVANTAGES | DISADVANTAGES |
|---|---|---|
| MMSE (5-10 min) | Tracks/quantifies changes; easy to administer; widely accepted; available in >50 languages | Not specific to AD or sensitive to mild dementia; influenced by age, education, and language skills |
| Mini-Cog (3 min) | Brief, easy to administer and score; unaffected by education, language skill; high sensitivity; easily paired with FAQ | |
| MoCA (10 min) | High sensitivity for MCI and mild AD; available in >20 languages; especially useful for patients with memory complaints but normal MMSE score | More time-consuming than other screening tools |
| AD 8 (3 min) | Administered in person or by phone; identifies earliest stages of dementia | Designed for informant, who may not be available, but can be given to patient |
| 7-Minute Neurocognitive Screen | Highly sensitive to early stages of AD | |
| AD, Alzheimer’s disease; FAQ, Functional Activities Questionnaire; MCI, mild cognitive impairment; MMSE, Mini-Mental State Examination; MoCA, Montreal Cognitive Assessment. | ||
The Mini-Mental State Exam is the gold standard
Considered the gold standard in dementia assessment, the MMSE is the most widely used cognitive screening tool in the United States.20 The MMSE samples 6 cognitive areas—orientation, registration, attention and calculation, recall, language, and constructional skill.21 It has a high degree of validity in detecting dementia, and is particularly useful in tracking and quantifying changes over time. Well-known features include the serial 7s, in which patients are asked to count backwards from 100 by 7s, and the 3-stage command: Take a paper in your right hand, fold it in half, and put it on the floor.
Besides being relatively short (testing takes 5-10 minutes), the MMSE is easy to administer. It has been translated into more than 50 languages, and can therefore be used in many cultural settings.
Interpreting the MMSE. A total score of ≤23 out of a maximum of 30 points is suggestive of dementia. However, patient performance on the MMSE is influenced by a number of factors unrelated to cognitive function, such as age, educational level, deficits in language skills, and motor or visual impairment.22 Thus, the cut point may be adjusted depending on the patient or population being screened, and the positive predictive value and sensitivity and specificity for dementia vary accordingly. In a population-based sample of >18,000 individuals with a cut point of 24, the sensitivity was 87% and the specificity was 82%.23
The usefulness of the MMSE is also limited because the test is not specific to AD and is not sensitive to mild dementia. When the test is used to screen highly intelligent, well-educated patients, it may fail to detect any decline in memory or cognitive function.
The Mini-Cog is a quick and easy alternative
The Mini-Cog screen consists of 2 simple components that evaluate executive function: a clock-drawing test and word recall.24 The patient is given paper and pencil and asked to draw a clock with hands set on a specified time—5:10, say. First, however, the screener recites 3 common but unrelated words; the patient is asked to recite the words before drawing the clock and to recall them afterwards. The entire test takes about 3 minutes.
Interpreting the Mini-Cog. Besides being quick and easy to administer, the Mini-Cog is easy to score:
- Patients who do not recall any of the words are classified as demented.
- Patients who recall all of the words are classified as nondemented
- Patients who recall 1 or 2 words are classified based on their clock drawing: They’re considered nondemented if the clock is normal and demented if it is not.
When clock-drawing is part of the Mini-Cog screen, the results are simply considered normal or abnormal. For a clock to be considered normal, all the numbers must be in the correct sequence and the hands correctly positioned to show the designated time.24 (The clock-drawing can also be used as an independent screen. For more about that, see “Clock-drawing: What to look for”.)