Researchers in eastern England developed a written test that was over 90% sensitive in detecting Alzheimer's dementia, and had specificity of 86%. (Sensitivity is the ability to detect the condition if it is actually present; specificity is how accurate the test is if the condition is not present—higher specificity means people without the condition are more likely to be labeled correctly.)
Because Alzheimer's can affect different brain functions, the test includes tasks that require different kinds of skills.
- Orientation--These questions concern the date and the subject’s name and birthdate.
- Short Term Memory--A sentence should be copied and memorized.
- Semantic Knowledge--Subject is asked the country’s top leader, and a historical date.
- Arithmetic
- Semantic Memory/Verbal Fluency--A list of creatures is needed.
- Abstraction--How are these items alike?
- Naming--Name the parts indicated.
- Visuospatial--Decipher a picture puzzle, and draw a clock face.
A score is also given for the amount of help the subject needed to complete the test.
The Study
The test was tried on 139 people with Alzheimer's dementia or mild cognitive impairment (which often turns to dementia), and 540 normal people, aged 18-95 years. Thirty one subjects with non-Alzheimer's dementia were also included. Subjects with dementia had been evaluated elsewhere—the new test was not part of their diagnostic evaluation.
As expected, the scores of all the normal subjects up to age 60 were about the same—there was no age drop off. However, beyond age 60, there was a significant drop is scores among normal subjects. An exception was semantic knowledge, which actually improved with age.
There was no gender difference in scores.
Compared to MMSE
The new test was compared to the Mini-Mental State Exam (MMSE), a widely used screening test. (The new test was much more sensitive; using a cut-off score of 23, the MMSE was only 52% sensitive. The researchers also pointed out that the MMSE usually takes more clinician time than the new test to administer.
Potential Weaknesses
The new test was developed in a community in eastern England; whether it is applicable to other locations and cultures needs to be determined.
The value of earlier detection of Alzheimer's is controversial. Early detection may have an impact on the person’s mood and quality of life, and may affect insurance fees and eligibility. For example, long term care insurance is sometimes not available to people who have been diagnosed with Alzheimer's, or if available, is at a higher rate.
On the other hand, early detection allows better planning, and the person and family can make decisions with better estimates of future needs. Also, legal decisions, such as wills and durable power of attorney, can be made while the person retains capacity (competency) to do so.
Source
BMJ 2009;338:b2030, doi: 10.1136/bmj.b2030 (Published 9 June 2009)
 |
