Blood tests for Alzheimer's have become good enough to pick up the disease process very early - so early, according to researchers at Lund University, that a positive result does not always explain why a patient is having memory problems. Their answer is to add a second marker, one tied to a later stage of the disease, alongside the widely used p-tau217 measurement.
The biology behind the problem is straightforward. Alzheimer's involves the buildup of amyloid-beta and tau, the protein that normally keeps the internal scaffolding of nerve cells stable. In the disease, tau is chemically altered into a form known as p-tau217 and begins forming tangles inside neurons. That altered protein can be detected in blood up to 20 years before symptoms appear, which is precisely what makes interpretation tricky.
Niklas Mattsson-Carlgren, who led the work and is a researcher at Lund University as well as a specialist physician at the memory clinic at Skane University Hospital, points out that more than 30 per cent of the elderly population shows some sign of Alzheimer's disease. A patient with mild cognitive complaints and a positive early marker may well have those symptoms caused by something else entirely - and a test that flags disease biology without confirming disease stage risks sending people down the wrong diagnostic path.
For memory clinics, that distinction matters practically: a marker linked to a later phase of the illness would help separate people whose symptoms are actually being driven by Alzheimer's from those carrying early biological changes that have not yet caused harm. The researchers frame the second marker as the more clinically useful of the two, which is a question of accuracy in real patients rather than detection speed alone.