Daijiworld Media Network - New Delhi
New Delhi, Sep 27: The US Food and Drug Administration (FDA) has cleared two new blood tests designed to help doctors assess whether people experiencing cognitive symptoms have brain changes associated with Alzheimer's disease, bringing the number of FDA-cleared blood tests for the condition to four.
The two newly cleared tests are PrecivityAD2, developed by C2N Diagnostics, and Elecsys Phospho-Tau (217P) Plasma (pTau217), developed by Roche in collaboration with Eli Lilly. The clearances were announced in August 2026.
The previously cleared tests are the Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio, cleared in May 2025, and the Elecsys pTau181 plasma test, cleared in October 2025.
Both new tests are intended to help identify amyloid pathology, one of the biological hallmarks associated with Alzheimer's disease. However, neither test is designed to diagnose Alzheimer's disease on its own. Results are intended to be interpreted along with a patient's symptoms, medical history and other clinical findings.
Blood-based biomarkers could provide a less invasive way of incorporating biological information into the assessment of people experiencing cognitive symptoms compared with traditional methods such as amyloid PET scans and cerebrospinal fluid (CSF) testing.
PrecivityAD2 is the first FDA-cleared Alzheimer's blood test indicated for symptomatic adults aged 40 and above. The test measures the amyloid-beta (Aβ) 42/40 ratio and the p-tau217/np-tau217 ratio and combines the results through an algorithm known as the Amyloid Probability Score 2 (APS2).
The test is intended for adults aged 40 years and older who have signs or symptoms of cognitive impairment and are being evaluated for Alzheimer's disease or other causes of cognitive decline. It is therefore not intended as a routine screening test for healthy people in their 40s.
In a clinical validation study involving 1,142 people with cognitive symptoms, PrecivityAD2 recorded a positive predictive value of 97.6% and a negative predictive value of 93.1% when compared with established reference methods, including amyloid PET scans and CSF biomarkers.
C2N said the FDA-cleared version of PrecivityAD2 is expected to become available later in 2026. The company currently offers a laboratory-developed version of the test under Clinical Laboratory Improvement Amendments (CLIA) regulations.
Doctors have also cautioned that the test's performance should be interpreted carefully in younger patients because relatively few people in their 40s were included in validation studies. A positive biomarker result can have significant implications for employment, family, finances and emotional wellbeing, making appropriate patient selection and follow-up important.
The second newly cleared test, Roche's Elecsys pTau217, measures the pTau217 biomarker in blood and is intended for adults aged 55 years and older who have signs, symptoms or complaints of cognitive decline.
Roche said the test is the first FDA-cleared single-biomarker blood test designed to support both rule-in and rule-out assessment of amyloid pathology in this age group.
The test provides positive, intermediate or negative results. These findings can help doctors determine whether further evaluation, including PET imaging or CSF testing, may be required.
Elecsys pTau217 is designed to run on Roche's existing cobas laboratory infrastructure. The company said more than 4,500 of its instruments are installed in laboratories across the US.
In a study involving more than 2,100 adults, results from the blood test agreed with amyloid PET findings in approximately 88% of people with cognitive impairment and 91% of those without cognitive impairment.
However, these figures do not mean that the test can independently diagnose Alzheimer's disease. Both Roche and C2N emphasise that their tests should be used as part of a broader clinical assessment.
The growing availability of blood-based biomarkers could potentially change how Alzheimer's disease is evaluated. Patients with cognitive symptoms may currently undergo cognitive and neurological assessments, brain imaging, laboratory tests and, in some cases, amyloid PET scans or CSF testing.
A blood test could help doctors determine whether a patient is more or less likely to have amyloid pathology before deciding whether additional, more invasive or expensive testing is necessary.
The tests could also help primary-care doctors determine whether patients require specialist evaluation. However, clinical assessment remains necessary to consider other possible causes of cognitive symptoms and to make decisions about diagnosis, staging and treatment.
The FDA has previously emphasised that Alzheimer's blood tests should be interpreted alongside other clinical information because false-positive and false-negative results can affect diagnosis and treatment decisions.
The new clearances reflect the rapid development of blood-based biomarkers for Alzheimer's disease and provide clinicians with additional options for assessing amyloid pathology.
While such tests could make biological assessment more accessible, questions remain about how they will be incorporated into routine clinical practice, how intermediate results should be handled and when confirmatory PET or CSF testing will still be required.
For now, the tests represent another step towards making Alzheimer's disease assessment more accessible through blood-based testing, while retaining the need for comprehensive clinical evaluation.