It comes as no surprise that a recent study showed a high error rate in the diagnosis of dementia when using brief cognitive screening tools. Incredibly, 35.7% of the sample 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). Frankly, I am astonished that AN is even considered to be a screening procedure. How can a single measure of cognitive functioning be used to support a diagnosis of dementia? It’s ridiculous.
In any event, the fact of the matter is that instead of referring patients for detailed neuropsychological testing, many clinicians routinely skip that step in the investigative process when making a diagnosis of dementia, relying instead on the results of a brief cognitive assessment, such as the MMSE. This research shows just how dangerous this omission can be. One can expect over a third of patients to be misclassified when this approach is used.
Of particular concern was the misdiagnosis rate in patients with subtle cognitive problems who were not actually demented. In patients with mild cognitive impairment (MCI), a false-positive diagnosis of dementia was made in 74.5% of patients when using the MMSE. False-positive diagnoses were 82.1% for the MIS and also 82,1% for AN for patients with MCI. That’s a scary error rate. Aside from the unnecessary alarm and fear triggered in the patient and family members by an incorrect diagnosis of dementia, these false-positive errors would have led to some patients being unnecessarily started on acetylcholine-esterase inhibitors.
The lesson is simple. Don’t take short-cuts when making a diagnosis of dementia. Detailed neuropsychological testing is mandatory in all cases of suspected dementia, not an optional extra.