A simple finger-prick blood test at home combined with online cognitive tests can reveal signs of Alzheimer’s disease, providing a convenient way to screen for early dementia.
The postal blood test, outlined in Nature Communications, is used to measure levels of two blood biomarkers linked with cognitive function: phosphorylated tau at amino acid 217 (p-tau217) and Glial Fibrillary Acidic Protein (GFAP).
It could provide a way to screen for dementia at home and act as a triage resource to identify those at risk earlier and tailor treatments more effectively, particularly in remote or unsupervised settings.
“This work raises the potential for screening people for their risk without the need for clinic visits or complex clinical assessments,” said lead researcher Anne Corbett, PhD, from the University of Exeter.
“It would ensure the people at highest risk could be prioritized for monitoring and diagnosis, unlocking the best support and treatment for those that need it most.”
While blood biomarkers are increasingly being used to diagnose Alzheimer’s disease, scalable tools are needed to reach the 99% of individuals with early cognitive impairment who are not seen in specialist healthcare services.
In an attempt to develop these further, Corbett and team conducted a study involving 174 people, of whom 146 had normal cognition and 28 had dementia.
All were participants in the PROTECT study, a larger investigation of more than 30,000 adults that aims to understand how healthy brains age and why people develop dementia.
Blood samples were collected at home using self-administered capillary blood tests, which were sent for p-tau 217 and GFAP lab testing. Venous blood samples were also available for 40 patients.
p-tau217 has previously been highly accurate at detecting Alzheimer’s disease pathology and is approved by U.S. regulators for symptomatic patients undergoing investigation for cognitive complaints.
GFAP is associated with broader cognitive decline and has been shown to be associated with Aβ deposition and progression of mild cognitive impairment to Alzheimer’s disease.
Brain performance tests were found to correlate with levels of both proteins, with p-tau217 showing the strongest association.
Capillary p-tau217 was significantly higher in people with dementia compared to those without and was significantly associated with cognitive performance and function.
A combination of an 85% specificity threshold for capillary p-tau217 85% and episodic memory performance one standard deviation (SD) below benchmarked norms identified 9% of participants who were at potentially high risk, and who also showed significantly higher impairment in cognition and function.
Importantly, this threshold for impairment of episodic memory indicated a much milder level of impairment than the 1.5 SD change required to identify people with mild cognitive impairment, revealing its potential ability to spot signs at a preclinical stage.
Unexpectedly, even though ptau217 and GFAP both identified individuals with cognitive impairment, there was only a modest overlap in individuals who were positive for both GFAP and p-tau217, with GFAP identifying a different group of at-risk individuals. GFAP biomarker appeared to be associated with vascular risk, unlike p-tau217.
Researcher Clive Ballard, MD, PhD, also at Exeter, said: “Our approach of combining our robust cognitive testing with measuring proteins via a postal blood test could provide a straightforward, efficient and cost-effective method to reach large numbers of people in the community who would not otherwise be prioritized for the next steps of diagnosis or support and to optimize the clinical pathway to enable early detection of those at highest risk.”
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