The current screening tools for mild cognitive impairment (MCI) result in a false-negative error rate of more than seven percent, say researchers at University of California, San Diego School of Medicine and Veterans Affairs San Diego Healthcare System.
The findings show that these individuals are misclassified as not having MCI based on standard screening instruments, but actually do have MCI once further testing is carried out.
MCI is a mild but noticeable and measurable decline in cognitive abilities, such as forgetting names and appointments or having a harder time navigating places. While these memory problems may not be significant enough to disrupt daily life, a clinical diagnosis of MCI indicates a greater risk of eventually developing dementia, including Alzheimer’s disease.
“There are consequences to misdiagnosis,” said first author Emily C. Edmonds, Ph.D., a postdoctoral fellow of neuropsychology in the Department of Psychiatry at University of California, San Diego School of Medicine.
“At the individual level, people incorrectly identified as cognitively normal might not receive appropriate medical advice or treatment. This could include preventive measures, such as diet or lifestyle changes to maintain cognitive function, or a referral to other health care providers.”
Furthermore, these misdiagnoses can also negatively impact research studies of MCI and early Alzheimer’s disease.
“If research participants are misclassified when they enroll in a study, this can weaken the study’s results, which makes it even more difficult to find and develop effective treatments or therapies.”
Currently, the widely used diagnostic criteria for MCI relies upon subjective memory complaints by the person being screened, a single test score indicating impaired memory, and clinical judgment.
Researchers say this diagnostic method can result in significant errors. They noted that their past research has also shown a high rate of “false-positives,” in which patients are diagnosed with MCI based on standard diagnostic criteria, but upon further testing, find that they do not actually have it.
“We have previously found that as many as one-third of MCI cases diagnosed with the standard method are false-positive errors,” said Edmonds. “This, coupled with our recent finding of a seven percent false-negative error rate, is concerning and tells us that the diagnostic criteria could be improved.”
For the study, researchers looked at data of 520 individuals participating in the Alzheimer’s Disease Neuroimaging Initiative, a nationwide, multi-institution study of MCI and Alzheimer’s Disease. The participants were almost evenly split by gender with a mean age of 74.3 years. They each underwent standard MCI screening and a more in-depth diagnostic process that involved additional memory and learning tests.
Just over seven percent (37 people) were identified as cognitively normal based on standard criteria, but qualified for MCI diagnosis after more advanced testing methods. In addition to mildly impaired cognitive performance, they also showed biomarkers in their cerebrospinal fluid indicating they are at-risk for future dementia. The rest of the participants tested normal using both methods — a true-negative rate of 92.9 percent.
The findings show that the use of rigorous diagnostic criteria that includes formal neuropsychological tests and less reliance on standard screening methods for MCI can better predict who is likely to progress from MCI to dementia and also improve clinical research studies.
The findings are published in the Journal of Alzheimer’s Disease.