The U.S. Food and Drug Administration has authorized the first blood‑based laboratory test intended to help diagnose Alzheimer’s disease. The Lumipulse G pTau217/β‑Amyloid 1‑42 Plasma Ratio, developed by Fujirebio Diagnostics, measures the concentrations of two proteins—phosphorylated tau 217 and β‑amyloid 1‑42—in a blood sample and calculates their ratio. A high or low ratio correlates strongly with the presence or absence of amyloid plaques in the brain, a pathological hallmark of Alzheimer’s. Until now, confirming amyloid required costly positron‑emission tomography (PET) scans or an invasive lumbar puncture to collect cerebrospinal fluid; the new test instead relies on a simple blood draw, potentially making evaluation faster, cheaper, and more accessible for patients.
Clearance was granted through the FDA’s 510(k) pathway after the agency determined that the assay is substantially equivalent to Fujirebio’s previously cleared cerebrospinal‑fluid β‑amyloid ratio test. The plasma assay also carried Breakthrough Device designation, which enabled accelerated review because Alzheimer’s is an irreversible, life‑threatening condition that affects nearly seven million Americans today and is projected to reach almost 13 million by 2050.
Indicated for adults 55 years and older who show signs of cognitive decline in a specialized care setting, the test’s performance was established in a multicenter study of 499 cognitively impaired participants. Compared with amyloid PET imaging or cerebrospinal‑fluid analysis, the assay correctly identified plaques in 91.7 percent of positive cases and correctly ruled them out in 97.3 percent of negative cases; fewer than 20 percent of samples returned indeterminate findings. These data suggest the blood test can reliably signal the presence or absence of amyloid pathology at the time of assessment.
As with any diagnostic, risks include false positives and false negatives. An erroneous positive result could cause psychological distress, spur unnecessary therapies, and delay identification of the true cause of symptoms. A false negative might postpone effective treatment or prompt redundant testing. Accordingly, the FDA stresses that the assay is not meant for population‑level screening or standalone diagnosis; clinicians must interpret results alongside each patient’s clinical picture, neurocognitive testing, and other imaging or laboratory data.
By enabling earlier, less burdensome detection of amyloid pathology, the Lumipulse G pTau217/β‑Amyloid 1‑42 Plasma Ratio represents a notable advance in the ongoing effort to diagnose—and ultimately treat—Alzheimer’s disease more effectively.