Blood Test Identifies Alzheimer’s in Minutes

Okay, here’s a breakdown of the key details from the provided text, focusing on the new Alzheimer’s blood test (APS2) and its implications:

What the Test Does:

Biomarkers: The test measures two key biomarkers in plasma (blood):
p-tau217 (phosphorylated tau 217): A specific form of the tau protein.
Amyloid Beta Ratio (Aβ42/Aβ40): The ratio of two forms of amyloid beta protein, linked to plaque formation in Alzheimer’s.
Probability Score: Combines these measurements into a single score representing the probability of Alzheimer’s-related biological changes in the brain, rather than just symptoms.
APS2 Algorithm: The algorithm blends the p-tau217 percentage with the amyloid ratio to estimate the chance of amyloid positivity in the brain.

Improved Diagnosis: The test considerably improves diagnostic accuracy, especially for primary care doctors. Primary care accuracy: 61%
Specialist accuracy: 73%
Reduces Unnecessary Testing: Can rule out Alzheimer’s biology, reducing the need for expensive and time-consuming imaging (like PET scans). Matches Existing Standards: The accuracy of the p-tau217 blood test closely matches that of more invasive cerebrospinal fluid (CSF) tests already approved by the FDA.
Cutoff Values: Using two cutoff values (one to rule in, one to rule out) further increases accuracy.
Intermediate Zone: Some patients will fall into an “intermediate zone,” requiring further testing (PET scan or repeat blood test) for clarity.

Relevance to Treatment:

Amyloid-Targeting Treatments: The test is crucial for determining if a patient has amyloid pathology, which is necessary before starting treatments like lecanemab (Leqembi) and donanemab (Kitty) that target amyloid.
FDA Approval: The FDA has approved both lecanemab and donanemab for early symptomatic Alzheimer’s disease, but only in patients with confirmed amyloid pathology.

How the test is administered:

* The test analyzes blood samples in batches or as they arrive, mirroring the workflow of typical clinics.

In essence, this blood test represents a significant step forward in Alzheimer’s diagnosis, making it more accessible, accurate, and efficient, and ultimately helping patients get the right treatment at the right time.