A study published in The Lancet Neurology has evaluated the accuracy of blood-based biomarkers in distinguishing Alzheimer’s disease from other neurodegenerative disorders, with findings suggesting a clinically viable role for plasma assays in routine diagnostics.
Researchers enrolled 786 participants across 17 memory clinics in Spain between 2016 and 2023. The cohort included patients with mild cognitive impairment or dementia of varying etiologies, as well as cognitively unimpaired controls. Researchers tested blood samples for three proteins linked to brain disease: phosphorylated tau217 (p-tau217), amyloid-β42/40 ratio, and neurofilament light chain (NfL). Results were compared with cerebrospinal fluid (CSF) and amyloid positron emission tomography (PET), which are the current reference tests but are invasive or costly.
Plasma p-tau217 was the most accurate marker, reaching an area under the curve (AUC) of 0.95 when distinguishing Alzheimer’s disease from healthy controls. Accuracy improved further when p-tau217 was combined with amyloid-β42/40 and NfL.
The blood tests matched well with CSF and PET results. They correctly identified 80-90 percent of Alzheimer’s disease cases and rarely confused Alzheimer’s with frontotemporal lobar degeneration or other dementias. Importantly, the tests performed consistently in both mild and more advanced disease stages.
Blood-based biomarker tests could make Alzheimer’s diagnosis easier, less invasive, and more widely available. They may also help laboratories offer earlier testing for patients with memory symptoms. However, the authors stress that more studies are needed in diverse populations before these assays can be widely adopted.
Standardization will be required, including defining cutoff values and integrating results into existing diagnostic workflows.
Overall, the study shows that automated blood tests, especially those measuring p-tau217, have strong potential to support the diagnosis of Alzheimer’s disease. While further validation is needed, the findings indicate that plasma biomarkers could reduce reliance on spinal taps or expensive brain scans in future diagnostic pathways.
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