The Blood Test That Might Correct Dementia's Misdiagnosis Problem

NEURODEGENERATIVE DISEASES | The mechanism that failed to distinguish FTD from Alzheimer's is being replaced by one that reliably can.

2026 T. Agnew

The rate of misdiagnosis or missed diagnosis in dementia care can approach 50%, with frontotemporal dementia (FTD) skewing the odds. Instead of presenting as symptoms of memory loss, FTD disease usually manifests as variations in personality and poor judgment, prompting families and doctors to identify it as depression, bipolar disorder, or another psychiatric issue.

For decades, closing that divide meant compiling a slow, resource-intensive team of neurologists, psychiatrists, neuropsychologists, and radiologists, all interpreting ambiguous evidence. As FTD research develops to better understand the disease, genuine breakthroughs are coming from blood.

Why Screening Tools Alone Is Never Enough

While the Mini-Mental State Examination (MMSE) is a sensible initial cognitive screen, its conceptualization failed to differentiate the origins of cognitive or behavioral shifts. A low score can reflect psychiatric illness, delirium, medication effects, or several specific neurodegenerative diseases uniformly. Frontotemporal dementia is the starkest illustration of the tool's limits: patients often possess flawless memory well into the disease's progress while declining in empathy, judgment, or social awareness, symptoms an MMSE and psychiatric assessment misses.

That diagnostic vagueness has dire repercussions. Treating a patient for Alzheimer's disease when frontotemporal dementia is the diagnosis slows appropriate care, raises caregiver burden, and can lead to irrelevant or even detrimental interventions — a cost absorbed by patients and health organizations.

How Blood Biomarkers Work

A 2026 JAMA Network Open study explored plasma biomarker patterns in early-onset Alzheimer's disease versus frontotemporal dementia and found disease-specific dynamics in phosphorylated tau 217 (p-tau217) and associated markers, distinct enough to help clinicians differentiate between the two conditions and track their progression over time — a distinction that standard behavioral screening alone often miss.

Plasma glial fibrillary acidic protein (GFAP), another marker under watchful eyes, detects early amyloid pathology with 85% sensitivity, often eight to ten years before clinical symptoms appear.

A February 2026 study in Nature Aging advanced this evidence beyond homogeneous populations where these biomarkers were first validated, confirming that blood-based AT(N) biomarkers — amyloid, tau, and neurodegeneration markers — provide accurate diagnosis when incorporated with cognitive and neuroimaging measures across genetically and ethnically disparate populations. For real-world distribution, that verification step matters immensely because a diagnostic tool that only works in the focused developed population isn't a diagnostic tool, but a scientific conclusion.

Related, a 2025 analysis of fluid biomarkers in familial FTD confirmed that mutations in genes like C9orf72, MAPT, and GRN generate detectable variations in blood and cerebrospinal fluid years before symptom onset, creating a course toward identifying at-risk patients before the behavioral changes trigger diagnosis, often only after progression of the disease.

What Changes for Interdisciplinary Care

A single blood test cannot replace a thorough dementia diagnosis that relies on a multidisciplinary evaluation comprising medical history, cognitive testing, medication review, neuroimaging, and caregiver knowledge. What blood-based biomarkers change is the sequencing and confidence of that process. Now, biomarker panels help direct which specialists a patient sees first, flag a likely FTD presentation months before psychiatric misdiagnosis occurs, and neurologists get a more accessible, fiscally responsible screening component instead of considering advanced neuroimaging or genetic testing for every ambiguous case.

For healthcare organizations creating dementia care pathways, the practical implications of the current biomarker evidence include:

●       Plasma p-tau217 and related markers can serve as an earlier differentiator for Alzheimer's versus FTD presentations, averting the need to wait for imaging or genetic testing to resolve uncertainty.

●       Validating any biomarker panel against the specific population it will serve, provided that diagnostic efficiency varied across genetically and ethnically diverse groups.

●       Treating blood-based screening as a starting place for multidisciplinary evaluation, not a replacement for it, biomarkers minimize the diagnostic question.

The Broader Strategy This Represents

Dementia analysis as precision medicine is moving in the same direction: away from a broad single disease label toward a set of biologically specific conditions identified through convergent evidence. Blood-based biomarkers don't erase the need for the interdisciplinary infrastructure that early dementia care recommended — they make that infrastructure more skillfully valuable at the entry point, detecting cases like frontotemporal dementia earlier and with better confidence than behavioral observation and a cognitive screening tool ever could alone. Lifestyle medicine depends on a multidimensional approach, and dementia diagnosis requires searching beyond memory. Now, with blood panels that detect underlying biological markers, it’s possible.

Sources & Further Reading

JAMA Network Open. “Plasma Biomarker Patterns Distinguish Early-Onset Dementia.” Kim, E.-J., et al., 2026.

Nature Aging. “Blood-Based AT(N) Biomarkers for Alzheimer's Disease and Frontotemporal Lobar Degeneration in Latin America.” Caviedes, A., Cabral, F., et al., 2026.

Frontiers in Neurology. “Fluid Biomarkers in Familial Frontotemporal Dementia: Progress and Prospects.” Guo, Qin, Cai, Wang, Luo, Yang, Feng, Gao, and Chen, 2025. DOI: 10.3389/fneur.2025.1663609.

ScienceDirect. “Blood-Based Biomarkers for Alzheimer's Disease: Advances in Early Detection and Monitoring of Age-Related Neurodegeneration.” 2026.

National Institute on Aging. “Alzheimer's Disease Facts and Figures.” 2025.

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