Screening tests for dementia

Only a tiny proportion of the laboratory and radiology tests identify potentially reversible causes of dementia. ¹ However, I would like to sound a note of caution against reducing the use of blood investigations like vitamin B₁₂, folate and thyroid function tests in practice.

In the largest study in terms of sample size ² the authors found that although a potentially reversible cause was found in only 4% of people with dementia overall, it rose to 19% when limited to people with a young-onset dementia. They also showed that concomitant conditions that were reversible, like vitamin B₁₂ deficiency and thyroid deficiency, were more frequent in patients with mild cognitive deficits than in those meeting the criteria for dementia. Although treatment of these conditions may not always lead to complete resolution of cognitive symptoms, it is important to identify any concomitant conditions in this group to prevent a misdiagnosis of dementia. The recent national dementia strategy ³ has also placed a strong emphasis on specialist assessment and accurate diagnosis.

I agree that subjecting a frail older person in their 90s with a clear history of insidious onset and gradually progressive memory loss to all the battery of investigations may be unwise, but I feel that these investigations should remain an intrinsic part of a comprehensive assessment of someone presenting with a mild cognitive impairment in their 70s or earlier.