Widely used dementia tests may give wrong diagnosis

In a new study at the University of Exeter, researchers found that quick tests used in primary care settings to identify whether people are likely to have dementia may often be wrong.

The tests called brief cognitive assessments, evaluate thinking and memory skills. They help doctors decide who may benefit from a full diagnostic assessment for dementia.

The first test examined in this study was the Mini-Mental State Examination, which looks at orientation to time and place and the ability to remember words.

The second was the Memory Impairment Screen, which focuses on the ability to remember words.

The third was Animal Naming, which involves naming as many animals as possible in 60 seconds.

The study found that all three tests often give incorrect results that may wrongly conclude that a person does or does not have dementia.

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.

In the study, 824 people in the United States with an average age of 82 were given full dementia assessments that included a physical exam, genetic testing for the APOE gene.

The gene is linked to a risk of Alzheimer’s disease, psychological testing, and comprehensive memory and thinking tests.

The researchers divided participants into two groups based on the comprehensive dementia diagnosis. Of the participants, 35% had dementia and 65% did not.

Participants took each of the three quick tests and researchers found that 36% of participants were wrongly classified by at least one of the tests, but only 2% were misclassified by all three tests.

Overall rates of misclassification by these tests individually ranged from 14% to 21%, including both false-positive and false-negative results.

The team also found that different tests had different biases.

One test had an education bias, in that 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.

Across all 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 of misclassification.

The researchers suggest that failing to detect dementia can delay access to treatment and support, whereas false alarms lead to unnecessary investigations, causing pressure on health care systems.

Identifying people with dementia in a timely fashion is important, particularly as new methods of treatment come onstream.

Their findings show that people desperately need more accurate and less biased ways of detecting dementia swiftly in a clinic.

A limitation of the study was that other brief cognitive assessments in clinical use were not examined.

The study author David Llewellyn, Ph.D., is from the University of Exeter Medical School in the United Kingdom.

The study is published in the Neurology Clinical Practice, an official journal of the American Academy of Neurology.

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Source: Neurology Clinical Practice.