A recent study showed a high rate of misdiagnosis of dementia when using brief cognitive screening tools. Concerningly, 35.7% of patients were incorrectly classified by at least one of the three screening procedures that were examined. The researchers looked at the well known Mini-Mental State Examination (MMSE), the Memory Impairment Screen (MIS) and animal naming (AN).
Animal Naming
The task simply requires the patient to name as many animals they can think of within one minute. While it can provide useful information, using a single that takes a minute to administer to make a diagnosis of dementia is ill-considered. Animal naming should not designated as a screening procedure. It’s simply too brief.
Skipping Detailed Testing
Instead of referring patients for detailed neuropsychological testing, many clinicians routinely skip that step in the investigative process when making a diagnosis of dementia. Instead, they rely on the results of a brief cognitive assessment, such as the MMSE or MoCA. This research shows just how dangerous this omission can be. Misdiagnosis occurs in a third of patients when using brief screening tools.
Misdiagnosis Rate in MCI
A very concerning finding was the misdiagnosis rate in patients with subtle cognitive problems. These patients do not actually have dementia and we use the term mild cognitive impairment (MCI) instead. Using the MMSE with MCI patients resulted in a false-positive diagnosis of dementia in 74.5% of patients. False-positive diagnoses were 82.1% for the MIS and also 82,1% for AN for patients with MCI. That’s an unacceptably high error rate.
Incorrect diagnoses cause unnecessary alarm and fear in the patients and family members. Furthermore, these false-positive errors may have led to some patients being started on medication (such as acetylcholine-esterase inhibitors) that they did not need.
Solutions
The lesson is simple. Don’t use screening procedures when making a diagnosis of dementia. Detailed neuropsychological testing is mandatory in all cases of suspected dementia, not an optional extra.
