Dementia: brief cognitive assessments often misclassify condition
BMJ 2018; 363 doi: https://doi.org/10.1136/bmj.k5047 (Published 29 November 2018) Cite this as: BMJ 2018;363:k5047
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The findings of this study is not surprising. MMSE has both floor and ceiling effects even when education levels are controlled. It does not test the frontal lobe functions too. As is well known, dementia is not diagnosed on the basis of a single cognitive rating scale score but requires a good history of progressive cognitive decline and its effect of activities of daily living. All reversible causes of cognitive decline has to be eliminated.
However, it does give a baseline indication of a patient’s cognitive performance and is useful in monitoring progression and staging of dementia during follow up which in turn helps determining what class of medication is used for treatment.
Competing interests: No competing interests
As a Podiatist researching Dementia, I am looking at the gait of Dementia patients with a view of picking up those with Normal Pressure Hydrocephalus (NPH). According to the BMA, NPH is also a misdiagnosed condition in the UK. It is estimated that up to 8-10% of dementia patients are suffering the reversible condition of NPH. Their gait is the prime indicator and cognitive assessment would not diagnose this condition.
Competing interests: No competing interests
Dear Editor,
Thank you for the synopsis. A Dementia diagnosis is not made on a brief cognitive test (or tests) but on a holistic assessment and collateral history of functional and cognitive decline over time. The assessment tests help to identify severity and possible unusual domain deficits (with interpretation taking into account the limitations of each test such as education level as identified in the article).
In regards to "Our findings show that we desperately need more accurate and less biased ways of detecting dementia swiftly in clinic" -- a good collateral history is usually better than almost all screening tests.
Just a reminder, these tests should not be used in a once off manner to make a diagnosis of a progressive cognitive decline (dementia).
Kind regards.
Competing interests: No competing interests
Re: Dementia: brief cognitive assessments often misdiagnose condition
As others have rightly pointed out our original article is not about the misdiagnosis of dementia. It would not be sensible or appropriate to diagnose dementia on the basis of a brief cognitive assessment alone.
Our paper is about the misclassification of dementia during initial investigations, particularly in non-specialist settings. In other words some people with dementia may be missed (false negatives) and some people without dementia may receive unnecessary additional investigations (false positives). Our article identifies the test specific biases that are inherent to brief cognitive assessments and emphasises the need to exercise caution when interpreting the results of these tests.
Our full article is freely available and can be accessed using this link: http://cp.neurology.org/content/early/2018/11/28/CPJ.0000000000000566
Further information: https://www.decodedementia.com/biases-in-cognitive-tests/
Competing interests: No competing interests