Novel blood sits at the center of this dementia and brain health question.
A novel blood marker discovered by researchers at Lund University is significantly reducing the risk of misdiagnosis in Alzheimer’s disease evaluation. The new marker, plasma eMTBR-tau243, works in combination with existing phosphorylated tau measures—particularly p-tau217—to distinguish between patients who truly have Alzheimer’s pathology versus those whose blood tests suggest brain changes that may never progress to clinical disease. This matters because phosphorylated tau levels alone have produced false positives: a patient might show elevated p-tau217 on a blood test but not actually meet the clinical criteria for Alzheimer’s disease, leading to unnecessary anxiety, premature labeling, and potentially premature treatment decisions. This article explores how the new marker works, what FDA-approved blood tests are available today, their limitations, and what these advances mean for anyone concerned about Alzheimer’s disease risk.
The timing of this breakthrough is significant. In 2025, the FDA cleared the first blood test designed for primary care use—Roche’s Elecsys pTau181—specifically to help rule out Alzheimer’s-related amyloid pathology in outpatient settings. While this represented a major milestone in making biomarker testing accessible, clinicians and patients both recognized that the science was still evolving to improve accuracy. The Lund University finding addresses that gap by offering a way to increase diagnostic certainty when elevated phosphorylated tau levels are detected.
Table of Contents
- How Does the New Blood Marker Improve Diagnostic Accuracy?
- Understanding Phosphorylated Tau and the False Positive Problem
- FDA-Approved Blood Tests and Their Current Role in Clinical Care
- Early Detection and the 20-Year Window
- What These Tests Cannot Do: Understanding Their Limitations
- The Role of Dried Blood Spot Testing and Accessibility
- The Future of Blood Biomarkers in Dementia Diagnosis
- Conclusion
- Frequently Asked Questions
How Does the New Blood Marker Improve Diagnostic Accuracy?
The new plasma eMTBR-tau243 marker represents a refinement in how researchers identify genuine Alzheimer’s pathology in blood samples. Blood-based biomarkers work by detecting proteins that accumulate in the brain during Alzheimer’s disease—specifically amyloid-beta, tau, and phosphorylated forms of tau. When brain cells break down or are damaged, these proteins leak into the cerebrospinal fluid and eventually into the bloodstream, where they can be measured. The challenge has been that elevated levels of these markers don’t always predict clinical dementia; some people with biomarker evidence of Alzheimer’s pathology remain cognitively normal for years or even decades. The eMTBR-tau243 marker provides an additional layer of information that, when combined with p-tau217 measurements, helps clinicians distinguish between pathological Alzheimer’s changes that are likely to cause symptoms and those that may remain clinically silent.
Think of it like a confirmation test: a single blood pressure reading that’s slightly elevated might warrant follow-up, but when combined with other cardiovascular markers, you get a clearer picture of actual cardiovascular risk. In the same way, eMTBR-tau243 combined with p-tau217 offers greater specificity, meaning fewer false positives and more confidence in the diagnosis. This reduces unnecessary worry for patients whose elevated tau may represent a preclinical finding with uncertain clinical significance. The Lund University research demonstrates that this two-marker approach catches genuine Alzheimer’s disease cases while minimizing the false alarms that have previously concerned both patients and healthcare providers. This is particularly important in primary care settings where cognitive specialists may not be available to provide context or reassurance to patients who receive an unexpected positive biomarker result.
Understanding Phosphorylated Tau and the False Positive Problem
Phosphorylated tau (specifically p-tau217) has become one of the most reliable blood biomarkers for Alzheimer’s disease. Tau is a protein that stabilizes microtubules inside neurons; when tau becomes hyperphosphorylated (heavily tagged with phosphate groups), it tangles and destabilizes cells. This process is a hallmark feature of Alzheimer’s pathology visible in brain autopsies. Detecting phosphorylated tau in blood has been revolutionary because it indicates that tau pathology is actually occurring in the brain—something that couldn’t be measured without invasive cerebrospinal fluid collection or expensive PET imaging. However, elevated p-tau217 alone is not diagnostic of Alzheimer’s disease. Multiple research studies have shown that some cognitively normal older adults have elevated phosphorylated tau levels.
These individuals may be in a preclinical stage where Alzheimer’s pathology is accumulating in the brain but hasn’t yet caused cognitive symptoms. Others may never develop symptoms during their lifetime. This distinction matters enormously: telling a 65-year-old with intact cognition that they have “Alzheimer’s-related brain changes” based solely on a positive p-tau217 test can trigger significant psychological distress, prompt medication use that may not be indicated, and lead to unnecessary specialist appointments. The addition of eMTBR-tau243 helps resolve this uncertainty by identifying which elevated p-tau217 cases are likely to progress to cognitive impairment and which may represent a stable preclinical condition. It’s important to recognize that this is not a limitation of the science but rather a reflection of how Alzheimer’s disease actually develops in humans. Brain pathology and clinical symptoms are not perfectly synchronized. The new combination approach acknowledges this biological reality rather than oversimplifying it.
FDA-Approved Blood Tests and Their Current Role in Clinical Care
The landscape of blood-based Alzheimer’s testing changed in 2025 when the FDA cleared Roche’s Elecsys pTau181 blood test for primary care use. This was the first FDA-authorized blood test specifically designed to help physicians rule out Alzheimer’s-related amyloid pathology in patients with cognitive concerns who are seen in office-based settings. The test is not intended to diagnose Alzheimer’s disease; rather, it helps determine whether amyloid pathology—one of the two main pathologic hallmarks of Alzheimer’s—is present or absent. A negative Elecsys pTau181 result can help a primary care physician reassure a patient whose cognitive concerns may have other causes: medication side effects, thyroid dysfunction, depression, sleep disorders, or simply normal aging. This reduces unnecessary referrals to neurologists and expensive cognitive testing. A positive result suggests that amyloid pathology is present, but it does not indicate whether the patient has mild cognitive impairment, dementia, or is in a preclinical stage.
The FDA clearance came alongside updated Alzheimer’s Association clinical practice guidelines released in 2025 that defined the appropriate use of blood-based biomarkers in clinical practice. The distinction between these tests matters in everyday practice. A primary care physician might offer the pTau181 test to a 70-year-old complaining of occasional forgetfulness as a way to determine next steps. If negative, that conversation often ends with reassurance. If positive, the physician knows to consider referral to neurology or dementia specialists. The newer eMTBR-tau243 marker, once it becomes commercially available, will add specificity to this pathway—helping secondary care providers further stratify risk among those with positive amyloid or phosphorylated tau findings.
Early Detection and the 20-Year Window
One of the most significant implications of blood-based biomarker research is the ability to detect Alzheimer’s pathology years or even decades before clinical symptoms appear. Multiple research groups have demonstrated that blood-based biomarkers can identify signs of Alzheimer’s-related brain changes up to 20 years before cognitive decline becomes noticeable. This creates a fundamentally new window for potential intervention: rather than waiting for a patient to develop memory problems before testing and diagnosing, clinicians can now identify high-risk individuals in a preclinical phase. This timeline creates both opportunity and complexity. On the opportunity side, identifying preclinical amyloid or tau accumulation opens the possibility of disease-modifying treatments started before significant neurodegeneration occurs.
Recent Alzheimer’s drugs like lecanemab target amyloid accumulation and appear most effective when given to patients with cognitive impairment or measurable cognitive decline, not to cognitively normal preclinical cases. However, this landscape may shift as new treatments are tested specifically in preclinical stages. On the complexity side, identifying someone as having pathological changes 20 years before symptoms raises difficult questions about how to counsel that person, whether treatment is appropriate, and how to avoid unnecessary medicalization of what might be a stable condition. For individuals with cognitive concerns today, blood biomarker testing represents an opportunity to get answers without the inconvenience and cost of specialist evaluation or PET imaging. A simple blood draw at a primary care visit can now provide information that previously required a referral, expensive neuroimaging, or months-long waiting lists. For those with a family history of Alzheimer’s disease or other dementia, blood biomarkers may eventually allow for earlier identification and entry into prevention trials, though such screening is not yet routine clinical practice.
What These Tests Cannot Do: Understanding Their Limitations
While advances in blood-based biomarkers represent genuine progress, it’s essential to understand what these tests cannot accomplish. A positive blood biomarker result is not a diagnosis of Alzheimer’s disease. Alzheimer’s disease, in its clinical sense, is defined by the combination of amyloid or tau pathology plus cognitive impairment. A positive biomarker in an asymptomatic person indicates pathological changes but not disease in the clinical sense. This distinction has major implications for how results should be communicated and what should happen next. Additionally, blood biomarkers identify a specific pathology—amyloid-beta and phosphorylated tau accumulation associated with Alzheimer’s disease—but they do not rule out other causes of dementia or cognitive impairment.
A patient with a positive Elecsys pTau181 test and ongoing cognitive decline might have mixed pathology: Alzheimer’s changes plus vascular dementia, Lewy body disease, or frontotemporal dementia. Blood testing for those conditions is more limited, and clinical evaluation, sometimes including MRI or PET imaging, remains necessary. Furthermore, these tests are designed and validated primarily in older adults; their interpretation in younger individuals or in patients with atypical presentations is less established. Another important limitation: blood biomarkers do not indicate the trajectory or prognosis of brain changes. Two people with identical p-tau217 and eMTBR-tau243 results might have very different cognitive futures—one might progress rapidly to mild cognitive impairment while the other remains stable for decades. Additional factors including age, presence of APOE4 genetic variants, systemic health, and other unmeasured variables influence outcomes. The tests provide information about pathology but not certainty about individual prognosis.
The Role of Dried Blood Spot Testing and Accessibility
Research published in Nature Medicine has demonstrated that minimally invasive dried blood spot testing—where patients provide a small blood sample on special filter paper rather than undergoing traditional phlebotomy—can detect Alzheimer’s disease pathology. This innovation could dramatically improve accessibility to biomarker testing, particularly in rural areas or regions where phlebotomy services are limited. A patient could collect their own sample at home and mail it to a laboratory, making Alzheimer’s biomarker screening feasible in settings where it’s currently impractical.
The clinical implications of dried blood spot testing include the potential for broader screening programs and the ability to offer biomarker testing to populations who currently have limited access to cognitive evaluation or specialist care. However, dried blood spot testing is still primarily in research settings. Clinical utility, standardization across laboratories, and insurance coverage remain to be established. When this testing becomes widely available in clinical practice, it could transform how Alzheimer’s risk assessment is approached—potentially allowing primary care physicians or even patients themselves to monitor biomarker status over time.
The Future of Blood Biomarkers in Dementia Diagnosis
The field of blood-based biomarkers for dementia is evolving rapidly. Beyond phosphorylated tau variants and amyloid-beta, researchers are investigating other proteins that might improve diagnostic specificity. The combination approach demonstrated by the Lund University research—using multiple markers to increase accuracy—is likely to become standard practice. Future blood tests may combine five, six, or more different biomarkers, creating a comprehensive “dementia signature” that not only identifies Alzheimer’s pathology but also distinguishes it from other dementia types.
The longer-term vision is personalized biomarker-driven diagnosis and risk stratification. Rather than a single binary test result, patients might receive detailed information about their amyloid burden, tau pathology, neuroinflammation, and neurodegenerative markers, all informing a nuanced assessment of dementia risk and the potential role for preventive or disease-modifying interventions. This shift from symptom-based diagnosis to pathology-based diagnosis parallels what has occurred in other fields: cancer diagnosis now routinely includes molecular subtyping, and cardiovascular risk assessment uses multiple biomarkers rather than a single cholesterol measurement. Dementia diagnosis is moving in the same direction, and blood-based biomarkers are central to that transformation.
Conclusion
The new plasma eMTBR-tau243 marker identified by Lund University researchers represents a meaningful advance in reducing false Alzheimer’s diagnoses. By combining this marker with existing phosphorylated tau measurements, clinicians can distinguish between patients with genuine Alzheimer’s pathology and those whose biomarker results may reflect a preclinical or stable condition. Combined with FDA-approved tests like the Elecsys pTau181 that bring biomarker assessment into primary care, these advances are making Alzheimer’s evaluation more accessible, accurate, and efficient.
If you have cognitive concerns or a family history of dementia, discussing blood biomarker testing with your primary care physician is now a reasonable option. If you receive a positive biomarker result, understanding what it does and does not mean—that it indicates pathological changes but not necessarily a diagnosis of dementia—is essential for informed decision-making. The field continues to evolve, and blood-based testing will likely play an increasingly central role in dementia detection and prevention efforts in coming years.
Frequently Asked Questions
If I have elevated p-tau217 but feel cognitively normal, do I have Alzheimer’s disease?
No. Elevated p-tau217 indicates that Alzheimer’s pathology is present in your brain, but without cognitive symptoms, you have not met the clinical definition of Alzheimer’s disease. Some people with preclinical pathology never develop symptoms during their lifetime. You should discuss findings with your doctor and may benefit from periodic cognitive testing to monitor for any changes.
How accurate is the new eMTBR-tau243 marker?
In Lund University research, the combination of eMTBR-tau243 and p-tau217 significantly improved the ability to distinguish genuine Alzheimer’s disease from false positives. However, the marker is still primarily in research settings and not yet widely available for clinical use. Ask your physician about availability in your region.
Can blood tests replace MRI or PET imaging in diagnosing Alzheimer’s disease?
Blood tests are increasingly useful for identifying Alzheimer’s pathology and can reduce the need for expensive imaging. However, brain imaging provides information about the extent and distribution of changes and can identify other causes of cognitive impairment. Your physician will determine which tests are appropriate for your situation.
What should I do if I have a positive blood biomarker result but no cognitive symptoms?
Discuss your results thoroughly with your healthcare provider. You may benefit from baseline cognitive testing to establish a reference point, lifestyle modifications known to support brain health (exercise, cognitive engagement, sleep, cardiovascular health), and periodic follow-up evaluation. Some individuals may be candidates for research studies or clinical trials.
Are blood biomarker tests covered by insurance?
Coverage varies by insurance plan, test type, and whether the test is ordered in a research or clinical setting. FDA-approved tests like the Elecsys pTau181 are more likely to be covered, particularly in primary care for patients with cognitive complaints. Check with your insurance provider regarding specific tests.
Can I request biomarker testing if I’m cognitively normal but worried about my risk?
This is an emerging area of practice. Some primary care physicians will order biomarker tests for cognitively normal patients with significant family history or personal risk factors, while others consider it premature without clinical symptoms. The 2025 Alzheimer’s Association guidelines provide some recommendations, but this remains an area where clinical practices vary. Discuss your specific situation and risk factors with your physician.
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For more, see NIH MedlinePlus — dementia.
