# New blood tests can spot Alzheimer's earlier than ever > Four FDA-cleared blood tests now detect Alzheimer's disease before symptoms appear, but doctors warn they're not for everyone. - Title: New blood tests can spot Alzheimer's earlier than ever · TIME - Summary: Four FDA-cleared blood tests now detect Alzheimer's disease before symptoms appear, but doctors warn they're not for everyone. Blood tests for Alzheimer's… - Keywords: alzheimer's disease, blood tests, fda approval, early diagnosis, biomarkers, tau protein, amyloid plaques, primary care, lecanemab, donanemab, cognitive decline, neurodegenerative disease - Source: TIME — https://time.com/article/2026/09/22/who-should-get-new-blood-tests-for-alzheimers-disease - Author: Alice Park - Published: 2026-09-22T12:00:04.001+00:00 - Read time: 3 min - Topics: alzheimer's disease, blood tests, fda approval, early diagnosis, biomarkers, tau protein, amyloid plaques, primary care, lecanemab, donanemab, cognitive decline, neurodegenerative disease ## Autopsy was the only proof For decades, doctors could only confirm Alzheimer's after death by examining the brain for amyloid plaques. Diagnosis relied on patient reports, cognitive tests, brain imaging, and spinal fluid tests, many subjective or invasive. ## Four blood tests now approved The FDA has cleared four blood tests to detect early signs of Alzheimer's disease. This marks a major advance in diagnosing the disease earlier and in more people. > This is a very exciting time for the field. We're going to start personalizing Alzheimer's care similar to cancer. ## First test: Fujirebio ratio test Cleared in May 2025, Fujirebio's test measures the ratio of beta amyloid and tau proteins to show if plaques are building up in the brain. But it requires specialized equipment and isn't widely available. ## Second test: Roche tau test FDA-cleared in October 2025, Roche's test detects tau levels linked to amyloid buildup. It's the first Alzheimer's blood test that primary care physicians can prescribe to rule out the disease. ## PrecivityAD2: younger patients included C2N's PrecivityAD2, cleared in August, uses mass spectrometry to detect amyloid and tau with a probability score. It's the first test approved for people as young as 40 showing cognitive problems. > Because of the ability to go after individuals who represent the earliest stages of the disease process, we now have the opportunity to provide early diagnosis. ## Roche ptau217 test most accurate Roche's Elecsys ptau217 plasma test, also cleared in August, detects a specific tau variant that appears when amyloid accumulates. Experts say it has the highest sensitivity and specificity of all available tests. > It's the most useful and has the highest sensitivity and specificity. ## Only for people with symptoms All four tests are designed for people already showing signs of cognitive problems or memory issues. They're not screening tools for healthy people with no symptoms. ## Doctors worry about misuse Experts caution against using blood tests in asymptomatic patients. Without cognitive symptoms, these tests provide risk information, not definitive answers, and could lead to unnecessary anxiety. > I worry about them being used inappropriately, especially in patients without symptoms. ## No data on healthy populations yet Blood tests haven't been studied in people without cognitive problems, so we don't know if they'd have unacceptably high false positive or negative rates. Looking for Alzheimer's proteins in lower-risk people tends to produce more false readings. ## Drug trials could change everything Two large studies are testing whether Alzheimer's drugs lecanemab and donanemab can slow disease in people without memory problems but with abnormal brain proteins. Results in about a year could make blood tests critical for early screening. ## One third may have biomarkers Research shows about a third of cognitively intact people above a certain age have positive Alzheimer's biomarkers on blood tests. If drugs prove effective, these tests could identify people at risk before symptoms appear. ## Tests track drug effectiveness Blood tests can monitor how well Alzheimer's medications work. A Korean study found patients on lecanemab showed drops in ptau217 levels three to six months after starting, linked to slower cognitive decline. ## Primary care doctors can now diagnose Blood tests put Alzheimer's diagnosis in the hands of primary care physicians, not just specialists. Studies show primary care doctors can interpret and manage Alzheimer's diagnoses using these tests. > Blood biomarker tests are democratizing the diagnosis of Alzheimer's disease. ## Alzheimer's Association sets guidelines The Alzheimer's Association recommends doctors first confirm cognitive symptoms, then rule out other causes like depression, medications, vitamin deficiencies, and sleep disorders before ordering blood tests. > A lot has to be done before patients should be getting a blood test for Alzheimer's. ## Key takeaway Blood tests for Alzheimer's are a major advance for people showing cognitive symptoms, but they're not screening tools for healthy people, yet.