Researchers in the United States have shown that a simple blood test can flag Alzheimer’s‑related proteins in adults in their early sixties, while a separate trial in North America demonstrates that an experimental PET tracer detects tau deposits more accurately than current scans. Both breakthroughs, reported in separate papers in The Lancet , could enable diagnosis long before memory loss becomes apparent .

Blood‑based biomarkers identified in 1,350 middle‑aged adults

In the first study, scientists measured amyloid‑beta and phosphorylated tau levels in the plasma of 1 ,350 dementia‑free participants with an average age of 61. According to the paper, higher concentrations of these proteins correlated with poorer performance on cognitive tests, suggesting that the blood markers reflect early brain changes.

The test,already cleared by the U.S. Food and Drug Administration, is not yet part of NHS services, but experts say FDA approval could pave the way for British rollout. Dr Richard Oakley of the Alzheimer’s Society called the approach “promising, cost‑effective and less invasive,” while Professor Paresh Malhotra of Imperial College warned that a positive result alone does not constitute a clinical diagnosis.

Experimental PET tracer MK6240 outperforms Flortaucipir in 682 participants

The second Lancet paper compared two PET imaging agents in 682 volunteers from the United States and Canada.. Researchers used the experimental tracer MK6240 to visualise tau protein aggregates and found it detected pathology more reliably than the standard Flortaucipir tracer currently used in Europe and the U.S.

By improving the signal‑to‑noise ratio, MK6240 could identify tau accumulation before patients experience noticeable cognitive decline, a step that may help clinicians confirm early disease when blood tests raise suspicion.

Potential boost for donanemab and lecanemab NHS approval

Both breakthroughs could strengthen the case for NHS funding of Eli Lilly’s donanemab and Eisai’s lecanemab, drugs that slow progression in early symptomatic Alzheimer’s by up to six months. The medicines were licensed in the UK in 2024 but were initially rejected by NICE on cost grounds; the manufacturers are currently appealing the decision.

Early detection through blood or PET could demonstrate that patients are treated at a stage when the drugs are most effective, potentially tipping the cost‑benefit analysis in favour of NHS adoption.

What remains uncertain about widespread screening?

Key unanswered questions include whether plasma biomarkers can reliably predict dementia in people without any cognitive complaints, and how the new PET tracer will perform in routine clinical settings outside research centres. As Professor Malhotra notes, “we only really understand what these tests mean when there is evidence of cognitive impairment.”

Additionally, the long‑term health economics of mass screening—balancing test costs, follow‑up imaging, and drug expenses—have yet to be modelled for the UK health system.