FDA clears 2 new Alzheimer’s blood tests, including one for adults as young as 40

C2N Diagnostics’ PrecivityAD2 uses a combination of amyloid and tau biomarkers. The test measures the amyloid-beta (Aβ) 42/40 ratio and the p-tau217/np-tau217 ratio, combining these measurements into an algorithm known as the amyloid probability score 2 (APS2).

The FDA-cleared test is indicated for adults ages 40 and older who have signs or symptoms of cognitive impairment and are undergoing evaluation for Alzheimer’s disease or other causes of cognitive decline. As such, this does not mean that the test is intended for routine Alzheimer’s screening of healthy adults in their 40s.

C2N highlights that the test is the first FDA-cleared Alzheimer’s blood test indicated for symptomatic adults beginning at age 40, which is notable because younger people can also develop Cognitive impairment and early-onset Alzheimer’s disease.

In a clinical validation study involving 1,142 people with cognitive symptoms, the test had a positive predictive value of 97.6% for a positive result and a negative predictive value of 93.1% for a negative result, when compared with established reference methods, including amyloid PET scans or CSF biomarkers.

Importantly, C2N states that PrecivityAD2 is not intended for use as a screening or stand-alone diagnostic test. The FDA-cleared version is expected to become available later in 2026. C2N currently offers a laboratory-developed version of PrecivityAD2 under CLIA regulations.

“The potential benefit is that symptomatic younger adults may be able to reach an explanation for their cognitive concerns much earlier, rather than spending months or years moving through referrals and more invasive testing before Alzheimer-related pathology is seriously considered,” Dung Trinh, MD, internist, of MemorialCare Medical Group and Chief Medical Officer of Healthy Brain Clinic in Irvine, CA, who is not involved with either blood test, noted to Medical News Today.

“That could be especially valuable in selected patients with progressive or unexplained cognitive symptoms, but the test is not intended as a screening tool for healthy people in their 40s. The challenge is that Alzheimer-related amyloid pathology is less common at younger ages, so the pre-test probability is lower, and interpretation becomes even more dependent on the broader clinical picture.”
— Dung Trinh, MD

“Younger adults also have a wide range of other possible causes of cognitive symptoms, including sleep disorders, mood disorders, medication effects, metabolic problems, and other neurological conditions,” Trinh pointed out.

“In addition, the number of very young patients included in validation studies has been relatively small, so clinicians should be cautious about assuming that performance estimates derived from the overall study population apply identically to people in their 40s,” he said.

“Because a positive biomarker result at that age can have greater implications for work, family, finances, and emotional well-being, careful patient selection, counseling, and a clearly defined follow-up plan are particularly important,” he stressed.

The second newly cleared test, Elecsys pTau217, takes a different approach, measuring pTau217 in blood.

Roche says it is the first FDA-cleared single-biomarker blood test designed to support both rule-in and rule-out assessment of amyloid pathology in adults ages 55 and older with cognitive symptoms.

The test provides positive, intermediate, or negative results. Roche says these results are intended to help clinicians determine whether additional evaluation, such as PET imaging or CSF testing, may be appropriate.

The test is designed to run on Roche’s existing cobas laboratory infrastructure, with the company reporting that more than 4,500 of its instruments are installed in US laboratories.

For Elecsys pTau217, a study of more than 2,100 adults found that the blood test results agreed with amyloid PET results in approximately 88% of people with cognitive impairment and 91% of people without cognitive impairment.

However, these figures should not be interpreted as meaning that either test can independently diagnose Alzheimer’s disease. Both manufacturers emphasize that the tests should be used as part of a broader clinical assessment.

Trinh highlighted the importance of the single-biomarker blood test and its intended use across primary and specialty care.

“This is potentially very significant because the major advance is not simply another Alzheimer’s blood test, but the possibility of moving meaningful biomarker assessment much earlier into the diagnostic process and into primary care,” he emphasized.

He also said most patients will first see a primary care physician when they start experiencing concerning symptoms, but that clinically evaluating Alzheimer’s-related pathology often involves being referred to a specialist, and deeper screening involving PET scans and CSF tests.

“A blood test that can be used with defined cutoffs in both primary and specialty care could allow clinicians to identify patients in whom amyloid pathology is unlikely, recognize those who may need further confirmation, and fast-track those with results strongly suggesting amyloid pathology to memory specialists and treatment evaluation.”
— Dung Trinh, MD

“The key point, however, is that the blood test should function as a gateway within the diagnostic pathway rather than as the entire diagnosis: cognitive symptoms still need clinical evaluation, alternative causes need to be considered, and specialist assessment remains important for diagnosis, staging, imaging, and treatment decisions,” Trinh said.

He added that these tests can help family doctors assess the patient and measure their risk, and then either manage the care themselves or refer the patient to a specialist, if necessary.

The availability of increasingly accurate blood-based biomarkers could change the diagnostic pathway for Alzheimer’s disease. At present, people with cognitive symptoms may undergo cognitive assessment, neurological evaluation, brain imaging, laboratory testing, and, in some cases, amyloid PET or CSF testing.

A blood test could potentially help clinicians identify people who are more or less likely to have amyloid pathology before deciding whether more invasive or expensive testing is necessary.

In a press statement, Roche suggests that its test could help clinicians determine which patients may need additional testing or specialist referral.

However, while the availability and approval of blood biomarker tests are encouraging, they do not eliminate the need for clinical evaluation.

Following the approval of the first FDA-cleared blood test to help diagnose Alzheimer’s disease, the Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio, the FDA emphasized that Alzheimer’s blood tests should be interpreted alongside other clinical information, as false-positive and false-negative results can have consequences for diagnosis and treatment decisions.

“For a patient, the most important point is that these blood tests can meaningfully change how likely it is that Alzheimer-related amyloid pathology is present, but they do not by themselves make the full diagnosis of Alzheimer’s disease,” Trinh explained to MNT.

What a positive result may mean

“A clearly positive result means amyloid pathology is much more likely and may justify moving more quickly toward specialist evaluation, imaging, or treatment eligibility assessment, while a clearly negative result makes amyloid pathology less likely and may shift attention toward other possible causes of cognitive symptoms.”
— Dung Trinh, MD

“In practical terms, these tests are best viewed as powerful triage tools that help clinicians decide what should happen next, while intermediate or borderline results generally require additional evaluation rather than a simple yes-or-no conclusion,” he concluded.

The two new clearances reflect the rapid development of blood-based biomarkers for Alzheimer’s disease. With the addition of PrecivityAD2 and Elecsys pTau217 as tests, clinicians now have more blood-based options for assessing amyloid pathology.

The growing availability of these tests could make the biological assessment of Alzheimer’s disease more accessible. However, questions remain around how they will be incorporated into routine clinical care, how clinicians should interpret intermediate or uncertain results, and when confirmatory PET or CSF testing is still necessary.

For now, the new tests represent another step toward moving Alzheimer’s disease assessment from highly specialized procedures toward more accessible blood-based testing, while still maintaining the need for a comprehensive clinical evaluation.