Alzheimer’s disease moves closer to a blood test: progress, caution and new questions

When Alzheimer’s begins as a suspicion

Alzheimer’s disease rarely appears with noticeable symptoms from the outset. It often begins as a suspicion: a recurring lapse in memory, a conversation that becomes difficult to follow or an everyday task that suddenly feels harder. From there, a long and complex medical process begins. That is why research into blood tests capable of detecting biomarkers linked to the disease is generating so much interest and hope in the fight against it.

Until now, discussing an Alzheimer’s diagnosis has meant that patients and families have had to enter a delicate and uncertain process: symptoms that could be confused with other conditions, neuropsychological assessments and brain scans, and a long wait before being able to name what was happening.

The possibility of detecting signs associated with Alzheimer’s in a simpler way represents a significant change. Not because it makes the disease less complex, but because it introduces a faster and more accessible test into the diagnostic process, with less discomfort for the patient.

What happens before symptoms appear

One of the particularities of Alzheimer’s is that its development has a biological basis and is not defined solely by memory loss, but also by changes that occur in the brain long before the disease becomes apparent in everyday life. These include the accumulation of beta-amyloid and alterations in the tau protein. For years, detecting these changes and understanding what was happening in the brain required more complex examinations, such as a PET scan or a lumbar puncture. This advance does not replace that assessment, but it can provide useful information earlier and with less impact on the patient.

Results published in journals such as Nature Medicine and JAMA have strengthened interest in this milestone. Certain measurements based on p-tau217 have shown performance comparable to cerebrospinal fluid analyses and high accuracy in both primary and specialist care. What matters is not only the accuracy, but how the test can be integrated into clinical practice: as a tool to support diagnostic suspicion, select which patients require additional studies and avoid unnecessarily long diagnostic journeys.

Why earlier detection matters more than ever

There is a fundamental reason why this advance is particularly relevant now. In 2025, the European Union authorised Leqembi and Kisunla, two treatments intended for selected patients with early-stage Alzheimer’s and confirmed amyloid in the brain. This is the key point: early identification is no longer simply a matter of convenience; it may influence whether a patient can access one of these therapies in time.

An advance that requires caution

As with any scientific development, however, there are limitations. A blood test cannot diagnose dementia on its own or replace a clinical assessment. The FDA itself has warned about the risks of an incorrect result that could cause distress, delay the identification of the true cause or expose the patient to unnecessary treatment.

For this reason, clinical guidelines are moving forward cautiously. In 2025, the Alzheimer’s Association published clinical practice guidelines on blood-based biomarkers, focused on their use within the diagnostic process for people with cognitive impairment, particularly in specialist settings. The message is clear: these tests can provide value, but they must be integrated into a structured medical pathway, rather than used as indiscriminate screening or as an isolated response to any memory lapse.

The distinction may appear to be a minor technical detail, but it is fundamental. One thing is to use these studies to support the diagnosis of someone who already has symptoms and is being assessed by healthcare professionals. It is quite another to offer them widely as a preventive detection tool to people without cognitive impairment, where interpretation becomes far more delicate. What does an altered biomarker mean when there are still no symptoms? What follow-up should be provided? What psychological impact could it have?

The questions raised by earlier diagnosis

All these questions explain why diagnostic progress also opens up a healthcare, ethical and organisational debate. If these tests are introduced on a broad scale, health systems will need clear protocols: who should receive the test, how the result should be interpreted and when it should be confirmed using other techniques, as well as how the patient should be supported. Earlier detection only makes sense if it helps the system respond more effectively through clinical guidance, follow-up, intervention on risk factors and support for families.

Elecsys pTau217 reaches the first point of care

In May 2026, Roche obtained the European certification required to market Elecsys pTau217, a test developed with Eli Lilly that measures a plasma protein linked to the presence of amyloid. There is an important distinction: it is not limited to specialist settings and is also intended for primary care. In other words, the caution reflected in the guidelines now coexists with a technology that is moving closer to the first medical consultation. Its purpose is not to provide an isolated answer, but to give healthcare professionals an initial indication of the possible presence of the disease and help them decide which tests should be carried out next.

Training for a new healthcare landscape

For Universidad Mundae, advances such as this show where healthcare education is heading: towards scenarios in which technology arrives earlier and the data involved are more sensitive, while decisions require a more comprehensive view of the patient. Alzheimer’s is not only a diagnostic challenge; it also forces us to consider how information is interpreted, communicated and supported.

From new clues to better decisions

Alzheimer’s disease is moving closer to a blood test, but this development should not be presented as a closed promise. It is a genuine evolution with the potential to improve the patient experience, although it requires caution. Blood can offer new clues about what is happening in the brain: turning those clues into useful, safe and humane decisions is the real challenge.