Biases in Dementia Screening Tools


Brief cognitive tests are useful screening tools for dementia in the primary care setting; however, a study published in the journal Neurology Clinical Practice shows that 3 of the most commonly used tools each have biases that may lead to false negative results. 

In this study, using only 1 assessment, 36% of subjects (n = 824, average age 82) were misclassified as having (false positive) or not having (false negative) dementia. In contrast, using all 3 tools for an individual resulted in a misdiagnosis rate of 1.7%. 

False-negative results correlated most highly with a lack of informant-rated poor memory whereas false-positive results correlated most with age, nursing home residency, and non-Caucasian ethnicity. For people with more education, the Mini-Mental State Examination (MMSE) had higher false negatives and lower false positives. For people in nursing homes, the Animal Naming (AN) test had lower false negatives and higher false positives.

Of the patients in the study, 35% (n = 291) had adjudicated dementia diagnosis, 43% had cognitive impairments that were not indicative of dementia (n = 231) and 22% (n = 292) had no cognitive impairments.

“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, PhD, 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.”

“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 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.”


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