Docs not keen on blood test to screen for Alzheimer's now

Experts here say usefulness currently limited, given lack of available treatments

- Salma Khalik

Senior Health Correspondent A blood test that could tell if someone has Alzheimer's disease could be on the cards in the coming years, as researchers in Sweden have found that measuring two biomarkers in blood plasma can identify the condition more accurately than current tests.

The study tested blood plasma for the levels of two key abnormal proteins associated with Alzheimer's: phosphorylated tau 217 (ptau217) which is indicative of neurodegeneration, and beta-amyloid 42 which, when built up, is associated with Alzheimer's.

This blood test had an accuracy of 90 per cent or more in identifying people with Alzheimer's, which accounts for about 70 per cent of all dementia cases globally.

These results were published in the Journal of the American Medical Association (Jama) on July 28.

The p-tau217 biomarker was also studied by researchers at the National Neuroscience Institute (NNI) in early 2024. In this small pilot, 72 blood samples tested were found to have significant differences in levels of this biomarker in people with and without Alzheimer's.

NNI is now planning larger studies on patients with early cognitive symptoms to validate its earlier findings.

Associate Professor Adeline Ng, a senior neurologist at NNI, told The Straits Times: "The data gathered will help us understand ptau-217 levels in Singapore patients with Alzheimer's disease and mild cognitive impairment (the stage before dementia) and how levels change as the condition progresses." Diagnosis today is done with either positron emission tomography (PET) imaging or with cerebrospinal fluid. Such tests are either expensive or invasive.

Experts here say that even when a blood test is available, it should be used only for patients with symptoms, to differentiate Alzheimer's from other forms of dementia. This is because treatments currently available in Singapore treat only symptoms of the disease, and do not prevent it or slow down its progression.