January 23, 2019
Quick tests of memory and thinking skills are often inaccurate in determining who might be in the early stages of Alzheimer’s disease and other forms of dementia, according to a new report. The tests, called brief cognitive assessments, help doctors decide who may benefit from a full diagnostic assessment for dementia. But results are often biased and may lead to unnecessary workups and worry, the study found.
The study, in the journal Neurology, looked at three popular tests to assess memory and thinking skills: the Mini-Mental State Examination, which looks at orientation to time and place and the ability to remember words; the Memory Impairment Screen, which focuses on the ability to remember words; and Animal Naming, which involves naming as many animals as possible in 60 seconds.
“Our study found that all three tests often give incorrect results that may wrongly conclude that a person does or does not have dementia,” said study author David Llewellyn of the University of Exeter Medical School in the United Kingdom. “Each test has a different pattern of biases, so people are more likely to be misclassified by one test than another depending on factors such as their age, education and ethnicity.”
The study looked at 824 Americans whose average age was 82. All were given comprehensive dementia assessments that included a physical exam, genetic testing for the APOE-E4 gene, which is tied to an increased risk of developing Alzheimer’s disease, psychological testing and extensive memory and thinking tests.
Using the comprehensive examinations, researchers determined that 35 percent likely had dementia, and 65 percent did not.
All of the participants then took each of the three quick tests to assess dementia. The researchers found that about one in three of them were wrongly classified by at least one of the tests. Some were determined to have dementia by the quick tests, but likely did not have dementia — a “false-positive” diagnosis. For others, the quick tests suggested they did not have dementia, even though the comprehensive exams suggested they likely did — so-called “false-negative” results.
Researchers also found that each of the tests had biases. For the Mini-Mental State Examination, for example, those with higher education were more likely to be misclassified as not having dementia, and those with lower education were more likely to be misclassified as having dementia. Older age, having an ethnic background other than white and living in a nursing home also led to misclassification in the various tests. For all the tests, a lack of information on whether a family member or friend rated the participant’s memory to be poor resulted in an increased risk that the person would be misclassified.
“Failing to detect dementia can delay access to treatment and support, whereas false alarms lead to unnecessary investigations, causing pressure on health care systems,” said Dr. Llewellyn. “Identifying people with dementia in a timely fashion is important, particularly as new methods of treatment come onstream. Our findings show that we desperately need more accurate and less biased ways of detecting dementia swiftly in clinic.”
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Marc Flajolet, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.
Source: Janice M. Ranson, MSc, Elzbieta Kuzma, PhD, William Hamilton, MD, et al: “Predictors of Dementia Misclassification When Using Brief Cognitive Assessments.” Neurology: Clinical Practice Vol. 9, No. 1, November 28, 2018