Researchers at the University of Pittsburgh School of Medicine report in The Lancet that a brain imaging test can pick up tau tangles, one of the defining features of Alzheimer's disease, before symptoms emerge - and earlier than the approach currently used in clinical practice across the United States and Europe. The team compared two tracers, the compounds injected before a PET scan that bind to target proteins and make them visible on the image.
The comparison mattered more than expected. According to the study, the choice of tau tracer can change who tests positive, which in turn affects when the disease is detected and whether a patient qualifies for treatment. Two people with the same underlying biology could receive different answers depending on which compound a clinic happens to use.
Tau is the protein most closely linked to the symptoms patients actually experience and to the pace of future decline, said Tharick Pascoal, corresponding author, associate professor of psychiatry and neurology at Pitt and a behavioral neurologist at UPMC. Detecting it earlier and staging it more precisely, he said, would sharpen judgments about who is genuinely on an Alzheimer's trajectory.
That distinction has immediate practical weight. Clinical trials depend on enrolling people whose brains show the disease process the drug is meant to target, and misclassification dilutes results. As new anti-amyloid and future anti-tau therapies reach patients, Pascoal noted, the same precision could begin shaping everyday clinical decisions about who is treated and when.