The United States Food and Drug Administration (FDA) has cleared two more blood tests to help clinicians assess Alzheimer’s-related brain changes in people with memory and thinking problems.

“The World Health Organization estimates that more than 55 million people live with dementia worldwide, with nearly 10 million new cases each year”

The development could make an important part of dementia assessment less invasive and more available than brain scans or spinal-fluid tests.

But the promise comes with a limit. A blood test is not a diagnosis, and it does not replace a careful clinical assessment. For people living with cognitive symptoms — and for health systems already struggling to provide specialist dementia care — its value will depend on what happens after the result.

“The WHO has warned that dementia remains underdiagnosed globally. Families can spend months navigating referrals while symptoms worsen and care needs grow”

Alzheimer’s disease is the leading cause of dementia, a condition that progressively affects memory, thinking and daily functioning.

The World Health Organization estimates that more than 55 million people live with dementia worldwide, with nearly 10 million new cases each year. The burden is rising fastest in low- and middle-income countries, where diagnosis and support often arrive late, if at all.

What is happening

The FDA has cleared C2N Diagnostics’ PrecivityAD2 blood test for adults aged 40 and older who have symptoms of cognitive impairment and are being assessed for Alzheimer’s disease or other possible causes.

It has also cleared Roche’s Elecsys pTau217 test for adults aged 55 and older with signs, symptoms or complaints of cognitive decline.

Both tests look for biological signals associated with amyloid pathology: abnormal deposits of a protein called beta-amyloid in the brain. Amyloid is one of the key changes linked to Alzheimer’s disease, alongside abnormal forms of another protein, tau.

PrecivityAD2 combines measures of the amyloid-beta 42/40 ratio and a tau-related measure, p-tau217/np-tau217, to produce an Amyloid Probability Score. Roche’s test measures phosphorylated tau 217, or pTau217, in blood.

Neither result can independently establish that a person has Alzheimer’s disease. Dementia symptoms can arise from many conditions, including depression, sleep disorders, medication effects, thyroid disease, vitamin deficiencies, stroke and other neurological illnesses.

Why it matters

Until recently, confirming amyloid pathology usually required an amyloid PET scan or analysis of cerebrospinal fluid obtained through a lumbar puncture. Both can be difficult to access. PET scanning is expensive and unevenly available; lumbar puncture requires trained staff, patient consent and follow-up.

A blood test could help clinicians decide who is more likely to need specialist referral or confirmatory testing, and who may need a wider search for other causes of cognitive decline.

That matters because diagnosis is often delayed. The WHO has warned that dementia remains underdiagnosed globally, particularly in settings with few geriatricians, neurologists, memory clinics or imaging services. Families can spend months navigating referrals while symptoms worsen and care needs grow.

The new tests may also matter for younger adults with unexplained cognitive symptoms. PrecivityAD2’s clearance from age 40 acknowledges that cognitive impairment and, more rarely, young-onset Alzheimer’s can occur before later life.

It does not mean that healthy adults in their forties should be screened.

What drives the problem

Alzheimer’s is not caused by one factor alone. Age is the strongest known risk factor, but it is not a normal part of ageing. Genetics, cardiovascular health, education, social conditions and access to timely healthcare can all influence risk, diagnosis and outcomes.

The deeper problem is often not a lack of scientific tools. It is the gap between those tools and the people who need them.

Patients with lower incomes, people in rural areas, migrants, linguistic minorities and those without consistent primary care are more likely to face delayed assessment.

Symptoms may be dismissed as ordinary ageing, stress or family problems. In some communities, stigma can discourage people from seeking help until a person’s independence has already been severely affected.

A blood test may reduce one barrier. It cannot, by itself, provide a neurologist, memory assessment, brain imaging, counselling, home support or affordable treatment.

What works

A good dementia assessment starts with the person, not a laboratory result. Clinicians should take a history of the symptoms, speak where possible with a family member or carer, review medicines, assess mood and sleep, test memory and thinking, and investigate potentially reversible causes.

For people whose symptoms suggest Alzheimer’s disease, blood biomarkers may help guide the next step. A clearly negative result may make amyloid pathology less likely and shift attention towards other explanations.

A clearly positive result may support faster referral for specialist assessment, imaging or further testing. Intermediate results require caution and usually further investigation.

Evidence supports the use of blood biomarkers as part of this pathway. In the clinical validation study cited by C2N, involving 1,142 people with cognitive symptoms, PrecivityAD2 had a positive predictive value of 97.6% and a negative predictive value of 93.1% against amyloid PET imaging or cerebrospinal-fluid biomarkers. These figures apply to the study population and should not be treated as universal performance guarantees.

Roche reported that Elecsys pTau217 agreed with amyloid PET results in about 88% of people with cognitive impairment and 91% of people without cognitive impairment in a study of more than 2,100 adults. Agreement is not the same as a final clinical diagnosis.

Who is left out — and why

The immediate beneficiaries are likely to be patients already able to reach clinicians and laboratories with the necessary systems in place.

That leaves substantial gaps. In many countries, including Malaysia and much of the wider region, access to dementia specialists, PET scans and advanced biomarker testing remains concentrated in large urban centres and private and advanced healthcare settings.

A test that identifies a patient as likely to have amyloid pathology has limited practical value if confirmatory assessment, counselling and treatment are unaffordable or unavailable.

Older people without strong family support may struggle to attend repeated appointments. Rural patients may face travel costs. People with limited health literacy may not receive clear explanations of what a positive, negative or uncertain result means.

For working-age adults, especially those assessed for young-onset cognitive impairment, a poorly explained result can carry serious implications for employment, insurance, finances and family life.

Health systems must also guard against inappropriate commercial screening. These tests are intended for people with cognitive symptoms undergoing clinical evaluation — not for anxious, healthy people seeking a simple prediction of future dementia.

An authoritative warning

The FDA made the central point when it cleared the first blood test for Alzheimer’s assessment in 2025: results must be interpreted alongside other clinical information, because false-positive and false-negative findings can lead to inappropriate diagnosis or treatment decisions.

That caution is not a reason to reject the tests. It is a reason to use them properly.

A blood biomarker can answer a focused question like how likely is it that amyloid pathology is present?

It cannot answer every question that matters to a patient, including whether their symptoms are due to Alzheimer’s disease, how advanced any disease may be, what support they need, or which treatment is appropriate.

Policy and accountability

The rapid arrival of Alzheimer’s blood tests raises a policy question that reaches beyond laboratory approval: who will pay, who will order the tests, and what care will follow?

Governments and health services need clear clinical pathways before widespread use. These should set out who is eligible for testing, how results are communicated, when confirmatory PET or cerebrospinal-fluid testing is needed, and how patients are referred for specialist assessment and support.

They also need investment in the less visible parts of dementia care: trained primary-care teams, cognitive assessment services, geriatric and neurology capacity, carer support, community care and protection against financial hardship.

The WHO’s Global Action Plan on the Public Health Response to Dementia calls on member states to improve diagnosis, treatment and care while supporting carers and reducing stigma. Yet progress remains uneven. In many places, national dementia strategies exist on paper while specialist services and community support remain scarce.

What must change

The new blood tests offer a genuine opportunity to shorten part of a long and difficult diagnostic journey. For a person with worrying memory loss, the prospect of a simpler test may mean earlier answers and less uncertainty.

But earlier testing without accessible follow-up risks creating a new divide: patients who can convert a laboratory result into care, and those who cannot.

The public-interest test is therefore not whether blood biomarkers reach the market. It is whether health systems use them to deliver timely, understandable and equitable care.

Alzheimer’s assessment should not depend on a person’s postcode, income or ability to pay for specialist testing.