Diagnostic Blood Tests Signal a New Era for Alzheimer’s Disease

The following article is an opinion piece written by Dr. Ashton Harper. The views and opinions expressed in this article are those of the author and do not necessarily reflect the official position of Technology Networks.

Dementia affects over 57 million people worldwide, yet three-quarters of those affected remain undiagnosed. Even as the burden and prevalence of the disease continue to grow, meaningful diagnosis remains out of reach for the majority.

As the most common form of dementia, Alzheimer’s disease has long been difficult to diagnose, relying heavily on specialists who are in short supply and therefore difficult to access. With the emergence of new disease-modifying treatments that require biological confirmation for eligibility, the pressure on an already strained diagnostic pathway is only set to intensify.

But a wave of innovation in blood-based biomarkers is promising to ameliorate the burden. Progress in diagnostics is outpacing therapeutic development, offering a necessary head-start to establish the scalable infrastructure that will bridge the gap between the current diagnostic vacuum and access to new disease-modifying treatments.

With a series of regulatory approvals over the last 12 months, diagnostics are setting the stage for a new standard, where earlier, more accurate, and more accessible detection and tailored care are finally within reach.

The diagnostic vacuum

Until recently, the clinical diagnosis of Alzheimer's disease has relied on a limited toolkit. Pen-and-paper cognitive assessments, clinical history, and the exclusion of other causes have formed the backbone of diagnostic practice—tools that are subjective, specialist-dependent, and poorly suited to detecting a disease that begins its destructive path years before symptoms appear.

Definitive biomarker confirmation has required either cerebrospinal fluid (CSF) analysis via lumbar puncture, or amyloid PET imaging. Both are valuable diagnostic tools, but their reach is limited by high costs, limited availability, perceived invasiveness, and a dependence on specialist infrastructure that most healthcare systems cannot provide at scale.

The result is that biomarker-confirmed diagnosis has remained the preserve of a small minority, and the vast majority of those living with the disease never receive a diagnosis at all.

The consequences are far-reaching. Diagnosis shapes who gets access to care, who qualifies for clinical trials, and ultimately who will benefit from the next generation of treatments.

Without it, health systems are left funding unnecessary investigations, misattributed diagnoses, avoidable crisis presentations, and emergency hospitalizations that place an additional burden on already stretched services. Accessible, accurate biomarker testing has long been the missing piece of the puzzle—until now.

Blood-based biomarkers: a revolution in diagnosis

The biomarker tests approved recently detect and measure proteins in the blood that reflect the underlying pathological processes of the disease, including the accumulation of amyloid plaques and tau tangles that are its defining hallmarks. In doing so, they offer new opportunities to triage and diagnose patients earlier, efficient screening for clinical trials, and access to tailored support and care.

Several biomarkers have emerged as clinically significant. pTau181 offers high sensitivity for early pathology, making it well suited to ruling out disease in initial triage. ApoE4 carrier status testing provides important information on risk stratification. Carrying the Ɛ4 allele has been associated with a higher likelihood of developing Alzheimer's disease, lower average age at symptom onset, and faster cognitive decline. Published evidence also indicates that ApoE4 carriers experience a higher incidence of amyloid-related imaging abnormalities (ARIA) during treatment with monoclonal anti-amyloid antibodies than non-carriers.

pTau217 has also emerged as a powerful diagnostic tool, matching the accuracy of CSF-based diagnostics when benchmarked against amyloid PET, all with the simple convenience of a routine blood draw.

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Critically, Roche's version of the pTau217 test is approved for use across the full breadth of care settings. The aim of integrating tests such as this outside specialist settings is to achieve pathway efficiencies and reduce the current referral bottleneck issues that plague the diagnostic journey for many patients and families. And because testing can be delivered on existing laboratory infrastructure available in most large labs, implementation requires no specialist equipment or significant additional investment.

For the first time, meaningful diagnosis is within reach for patients who would previously never have accessed it, including those in rural areas and those in socioeconomically disadvantaged communities far from specialist centers.

The clinical community is moving quickly to formalize how these tests should be used. In 2025, the Alzheimer's Association published its first Clinical Practice Guideline on blood-based biomarkers in specialty care—the first formal, evidence-based recommendations on their use in clinical practice.

The guidelines recommend blood-based biomarker testing as part of routine diagnostic workup for patients presenting with cognitive impairment across neurology, geriatrics, psychiatry, and memory clinic settings—both as a triage tool to rule out Alzheimer's pathology, and, if sufficiently accurate, as a confirmatory test to rule it in.

As these tests become available in non-specialist settings across the world, equivalent guidance will be essential to equip general practitioners and general hospital physicians with the clinical frameworks they need to interpret and act on results confidently.

A major milestone toward this goal was reached at AAIC 2026 with the showcasing and publication of the “Decision Support Tool for the Use of BBMs for Alzheimer’s Disease Pathology in Primary Care,” a framework designed to directly guide frontline primary care clinicians.

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Furthermore, the next iteration of the Alzheimer's Association Clinical Practice Guidelines is expected to formalize recommendations for primary care, marking a significant step towards embedding blood-based biomarkers into mainstream medicine.

The profound impact of providing primary care doctors with these tools was underscored by a landmark Swedish study presented at the conference. In a study of more than 1,300 patients and 165 physicians, family doctors who reviewed blood test results diagnosed Alzheimer’s correctly 93% of the time—nearly identical to specialists’ 94% accuracy among the same patients. Before seeing the blood test results, family doctors were accurate just 65% of the time (compared to 76% for specialists); the blood test closed that diagnostic gap almost completely.

Moving forward, studies in Australia and Scotland will evaluate the clinical utility of pTau217 in primary care settings, and their findings will continue to build the robust evidence base on which future iterations of these guidelines will depend.

What is becoming clear is that the future of Alzheimer's diagnostics lies not in one definitive test, but in a growing portfolio of validated tools, each one potentially optimized for a distinct purpose across the care pathway, from initial triage through to diagnostic confirmation, and, as the science continues to advance, staging, prognosis, and treatment monitoring.

In the future, the hope is that, when used together, they will offer a level of diagnostic precision, accessibility, and clinical utility that was simply not possible before. Realizing the full potential of this toolkit will require standardization across platforms and assays to ensure results are comparable and reliable wherever testing takes place.

Why diagnosis matters

For patients and families, a timely and clear diagnosis is a critical step on the disease journey, enabling proactive legal, financial, and care planning. Perhaps most importantly, it allows people to make sense of potentially frightening changes that may have gone unexplained for years. The value of knowing should not be underestimated.

The clinical stakes are equally high. A new generation of disease-modifying therapies is emerging that target the underlying biology of Alzheimer's to slow its progression, and they are most effective early in the course of the disease, when intervention can also prolong functional independence. Biomarker confirmation is increasingly a prerequisite for accessing them, making timely, accurate diagnosis not just clinically valuable but therapeutically critical.

Exclusion is just as important as confirmation. Identifying amyloid-negative patients prevents misattribution of cognitive decline and enables investigation of alternative causes, with significant implications for subsequent management and health system efficiency.

Accessible testing also opens up new prognostic possibilities. Patients with elevated plasma pTau217 who present with mild cognitive impairment progress to overt Alzheimer's dementia at a significantly accelerated rate compared to those who test negative—a signal with immediate value for counseling, care planning, and the prioritization of intervention. And serial testing becomes feasible through blood draws alone, removing the need for repeated invasive procedures.

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Blood-based biomarkers are also transforming clinical trial recruitment. Confirming amyloid pathology in potential participants has historically meant relying on expensive PET scans or invasive lumbar punctures. This is a slow, costly bottleneck with high screen failure rates that has made Alzheimer's trials among the most expensive and difficult to recruit for in medicine.

The TRAVELLER study is an example of how blood-based biomarkers can help overcome that barrier. Using a simple blood test alongside a brief clinical assessment to pre-screen participants for Phase 3 Alzheimer's trials before any invasive or expensive procedures are required has enabled broader community outreach and extended access to more diverse populations. To date, the study has reached over 10,000 people across the globe.

Diagnostics: setting the stage for a new era of Alzheimer’s disease management

Innovation in diagnostic biomarkers continues to outpace progress in therapeutics, creating an invaluable opportunity. The tests now available enable early detection, support trial recruitment, and make treatment monitoring feasible in routine clinical practice.

Blood-based biomarkers also enable real-world evidence generation at scale, powering datasets that can refine our understanding of disease progression and identify the patients most likely to respond to treatment.

ApoE4 genotyping is already demonstrating what biomarker-guided treatment selection looks like in practice—the first example of its kind in Alzheimer's disease, and a sign of what is to come as therapeutic pipelines advance.

The challenge now is to ensure that validated tests are adopted into routine practice at the speed and scale the disease demands, so that as new therapies arrive, the diagnostic infrastructure is already in place to identify the right patients, at the right time.

We are closer to that moment than we have ever been. Blood-based diagnosis is no longer experimental. It is the foundation on which the next era of Alzheimer's medicine will be built. And for the first time, a diagnosis and the care pathway that follows could be within reach for everyone who needs it.