Neurodegeneration Biomarkers: A Researcher’s Guide to Blood-Based Testing, Multiplex Panels and Assay Selection

• The best blood biomarkers for a neurodegeneration study depends on the biological question. pTau217 is currently one of the strongest blood biomarkers for Alzheimer’s-related pathology, while NfL primarily reflects neuroaxonal injury and GFAP reflects astroglial activation. Aβ42 and Aβ40 add amyloid-pathway information, whereas emerging markers such as brain-derived pTau, TDP-43 and LRRK2 address more specialized questions. Researchers studying more than one pathway can use multiplex panels, while a single-analyte assay may be preferable when one validated biomarker is the primary endpoint. Platform selection should then be based on the required sensitivity, plex, matrix, sample volume and validation—not simply on which technology claims the lowest detection limit.

Neurodegeneration research is moving rapidly from a search for one “best” biomarker toward combinations of fluid biomarkers that represent different aspects of disease biology. In Alzheimer’s disease alone, researchers can now investigate amyloid biology, phosphorylated tau, neuroaxonal injury, astrocytic responses and inflammation in blood or cerebrospinal fluid. At the same time, emerging biomarkers are expanding the toolbox for Parkinson’s disease, ALS, frontotemporal degeneration and age-related co-pathologies. [1]

Eve Technologies now offers a range of ultrasensitive MSD-based neurodegeneration assays that can be selected according to that question, including a new Early Access Human MSD Discovery Assay Neurodegeneration 7-Plex, conventional pTau217, Brain-Derived pTau217, Brain-Derived pTau181, and a Neurology 3-Plex measuring GFAP, NfL and total Tau. These can also be complemented by our established inflammatory cytokine testing capabilities.

Why neurodegeneration research increasingly needs more than one biomarker

Neurodegenerative diseases are biologically heterogeneous, and overlapping pathologies become increasingly common with age. A biomarker strongly associated with Alzheimer’s pathology does not necessarily describe the amount of axonal injury, astrocyte activation, inflammatory activity, Parkinson’s-related signaling or TDP-43 pathology present in the same sample. The revised Alzheimer’s criteria explicitly distinguish core disease biomarkers from more general markers of neurodegeneration and from biomarkers of coexisting pathologies.

That is why multiplex and complementary biomarker strategies are useful. Instead of asking a single molecule to describe an entire disease process, researchers can build a biomarker profile in which each analyte represents a different layer of biology.

For an Alzheimer’s-focused project, for example, pTau217 and amyloid-β measurements can interrogate core Alzheimer-associated pathways, while NfL can add information about neuroaxonal injury and GFAP about astrocytic responses. Longitudinal studies increasingly support the value of evaluating pTau217, GFAP and NfL together when investigating cognitive decline and disease progression.[2]

pTau217: a central biomarker for Alzheimer’s disease research

Phosphorylated Tau at threonine 217, or pTau217, has emerged as one of the strongest blood biomarkers associated with Alzheimer’s disease pathology. Plasma pTau217 is closely associated with amyloid and tau pathology and has repeatedly demonstrated strong performance in studies using CSF or PET reference standards. [3]

The 2024 revised Alzheimer’s criteria classify soluble phosphorylated tau species including pTau217, pTau181 and pTau231 as early-changing tau biomarkers, with pTau217 receiving particular emphasis among accurate plasma assays. Importantly, the criteria also warn that biomarker performance is assay-specific: measuring the same molecular target does not automatically guarantee equivalent analytical or clinical performance across methods. [1]

For research requiring a focused measurement of this biomarker, the Human MSD Discovery Assay pTau217 provides an ultrasensitive single-analyte option for serum, plasma and CSF.

What is brain-derived pTau217—and why does brain specificity matter?

Tau is strongly associated with neurons and Alzheimer’s disease pathology, but tau species measured in blood are not necessarily derived exclusively from the central nervous system. This has motivated the development of brain-derived tau assays designed to preferentially measure CNS-originating tau rather than peripheral contributions. Recent research suggests that this increased biological specificity can improve the relationship between blood tau measurements and underlying Alzheimer’s pathology. [4]

A 2026 head-to-head analysis of brain-derived pTau217 and total pTau217 found that BD-pTau217 provided superior performance for aspects of amyloid and tau pathology classification. Other studies are now investigating brain-derived pTau217 for prognostic stratification and longitudinal disease assessment. [4]

This does not mean that conventional pTau217 has become obsolete. Rather, the two assays can address somewhat different research needs.

Conventional pTau217 is backed by an exceptionally large and rapidly expanding evidence base and is highly useful for Alzheimer’s biomarker studies. Brain-derived pTau217 may be particularly attractive when a project is specifically concerned with CNS-derived tau signal, peripheral tau contribution, comorbidities or maximizing biological specificity to brain pathology.

Eve Technologies offers both approaches: conventional pTau217 as well as Brain-Derived pTau217 on the MSD platform, allowing study design to be driven by the biological question rather than by a single assay format.

Where does brain-derived pTau181 fit?

pTau181 has a longer history in Alzheimer’s biomarker research and remains an important tau phosphorylation site. Across many contemporary head-to-head studies, pTau217 generally demonstrates stronger discrimination of Alzheimer’s pathology than pTau181, although pTau181 continues to provide meaningful complementary information and may be valuable for comparison with historical datasets or studies specifically designed around T181 biology. [5]

Brain-derived pTau181 adds another dimension by applying brain-specific tau measurement to this established phosphorylation site. Human MSD Brain-Derived pTau181 assay, like its BD-pTau217 assay, is available for serum, plasma and CSF research samples.

For studies examining tau biology in depth, measuring conventional pTau217 alongside one or more brain-derived tau assays can therefore be more informative than treating every pTau measurement as biologically equivalent.

GFAP and NfL provide a broader view of neurodegeneration

Neurofilament light chain, or NfL, is widely used as an indicator of neuroaxonal injury. Because axonal damage occurs in many neurological diseases, NfL is valuable as a broad marker of neuronal injury rather than a specific identifier of Alzheimer’s disease. GFAP, in contrast, reflects astrocytic biology and is increasingly studied as a blood biomarker associated with astrocyte activation and Alzheimer-related changes. [6]

Their complementary roles make GFAP and NfL particularly useful alongside disease-associated biomarkers such as pTau217. A biomarker profile can therefore distinguish, conceptually, between evidence of Alzheimer-associated pathology and evidence of downstream or accompanying cellular injury and glial responses. [7]

For projects focused on this more compact neurodegeneration signature, Our MSD Discovery Assay Neurology 3-Plex simultaneously measures GFAP, NfL and total Tau. MSD reports fg/mL-range detection for its S-PLEX Neurology Panel.

A focused seven-marker view of neurodegeneration

For studies that need greater breadth without moving immediately to very high-plex proteomics, Our new Early Access Human MSD Discovery Assay Neurodegeneration 7-Plex measures:

GFAP | NfL | pTau217 | Aβ40 | Aβ42 | LRRK2 | TDP-43

from a 50 µL single-analysis sample volume.

The panel is useful because the seven analytes do not all describe the same biological process.

• pTau217 and amyloid-β provide an Alzheimer-focused layer.
• GFAP introduces astrocyte biology, while NfL provides a broader measure of neuroaxonal injury.
• LRRK2 expands the panel toward Parkinson’s disease-related molecular research.
• TDP-43 adds an emerging proteinopathy marker relevant to research in ALS, frontotemporal degeneration and age-related TDP-43 pathology.

The latter two biomarkers should be interpreted differently from established Alzheimer’s pTau biomarkers. LRRK2 is an important mechanistic and pharmacodynamic target in Parkinson’s disease research, while fluid TDP-43 biomarkers remain an active area of development and validation. For example, current Alzheimer’s criteria note that a confirmed disease-specific fluid biomarker for LATE has not yet been established.

That makes the 7-plex particularly interesting as a research panel spanning established and emerging neurodegeneration biology, rather than as a diagnostic panel.

When should researchers choose the 7-plex, a 3-plex, or a singleplex?

The right assay depends less on which panel contains the largest number of analytes and more on the study hypothesis.

Do not overlook neuroinflammation

Neurodegeneration and inflammation are deeply interconnected research areas. Microglial and astrocytic responses, peripheral immune activity, and cytokine signaling are being investigated across Alzheimer’s disease, Parkinson’s disease, ALS and other neurological disorders. [8]

This makes cytokine profiling a natural extension of neurodegeneration biomarker studies rather than a completely separate field.

Researchers interested in inflammatory mechanisms may wish to complement structural or disease-associated biomarkers with cytokines such as IL-1β, IL-6, TNF-α, IFN-γ, IL-10, IL-17A and related immune mediators.

Building the right neurodegeneration biomarker strategy

The growth of blood-based biomarker research does not mean that every neurodegeneration study should use the same marker or platform. pTau217 has become exceptionally important in Alzheimer’s disease, but pTau217, GFAP, NfL, amyloid-β, TDP-43, LRRK2 and inflammatory cytokines answer different biological questions.

That is why assay selection should begin with the research objective:

Biomarker biology comparison

Biomarker	What the measurement primarily represents	Where it is especially useful in research	Important limitation
pTau217	Tau phosphorylated at threonine 217; plasma concentrations are strongly associated with Alzheimer’s amyloid and tau pathology in multiple recent cohorts	Alzheimer’s pathology studies, cohort stratification, longitudinal biomarker research, head-to-head assay studies	“pTau217” is not one standardized assay. Different antibody designs and MS methods can produce different performance.
pTau181	Tau phosphorylated at threonine 181	Established Alzheimer’s biomarker research, historical cohort continuity, comparisons among tau phosphorylation sites	Frequently—but not universally—less discriminative than strong pTau217 assays; results remain method-dependent.
Aβ42/Aβ40	Relative abundance of amyloid-beta 42 to amyloid-beta 40	Studies of amyloid-associated biology; complement to pTau	Plasma differences can be small and method-sensitive; immunoassay and IP-MS performance should not be assumed equivalent.
NfL	Neuroaxonal injury	Longitudinal neurodegeneration studies and cross-disease research where neuronal injury is the endpoint of interest	Broad rather than Alzheimer’s-specific; concentration can change in several neurological disease contexts.
GFAP	Astrocytic activation/injury response	Alzheimer’s studies involving astroglial biology, amyloid-associated responses and complementary profiling with NfL/pTau	Less specific for Alzheimer’s pathology than pTau217 and elevated in other neurological states.
Total tau	Tau signal without restriction to a specific phosphorylation site	Broader tau/neural-injury research and selected preclinical designs	Blood total tau should not be treated as equivalent to pTau217 or pTau181.
TDP-43	Depends heavily on assay design: soluble/total protein, modified species or compartment-specific TDP-43	ALS, FTD and TDP-43-related exploratory research	Plasma total TDP-43 is analytically challenging: a 2024 study found that ≥95% of TDP-43 in platelet-containing plasma was localized to platelet cytosol, highlighting major preanalytical and source-specific concerns.
LRRK2	Abundance of leucine-rich repeat kinase 2; other assays can instead interrogate phosphorylation/kinase pathway activity	Parkinson’s-related pathway research and mechanistic studies	Total LRRK2 concentration does not by itself establish LRRK2 kinase activity or disease status; activity-oriented studies may require phospho-LRRK2/pRab readouts.

Why NfL and GFAP answer different questions

NfL and GFAP are valuable precisely because they are not substitutes for pTau.

NfL is a structural axonal protein released in association with neuroaxonal injury. In contrast, GFAP is an astrocytic intermediate filament and is commonly used as a marker of astroglial response. A study can therefore show a strong pTau217 signal with relatively modest NfL, or elevated NfL/GFAP without an Alzheimer’s-specific pTau profile, depending on the underlying biology.

Disease-by-biomarker research matrix

The matrix below describes research relevance, not diagnostic indication.

Research question	Higher-priority targets	Complementary or exploratory targets	What the combination can and cannot tell you
Alzheimer’s-associated amyloid/tau biology	pTau217; Aβ42/Aβ40	pTau181, GFAP, NfL	pTau/amyloid measurements address Alzheimer’s-associated pathology; GFAP/NfL add cellular-response and injury context.
Early/preclinical Alzheimer’s biomarker change	pTau217; Aβ42/Aβ40	GFAP; brain-derived pTau217/pTau181	Recent cohorts show strong early associations for pTau and GFAP, while BD-pTau remains an emerging, assay-specific research area.
Mixed dementia / overlapping pathology	pTau217 and/or amyloid markers to characterize AD-related signal	NfL, GFAP, TDP-43	Useful for multi-pathway profiling, but soluble TDP-43 is not equivalent to neuropathological confirmation of TDP-43 proteinopathy.
ALS / FTD-related injury	NfL	TDP-43, GFAP, inflammatory mediators	NfL measures injury; TDP-43 remains analytically and biologically form-dependent.
Parkinson’s-related pathway research	Hypothesis-specific assays	LRRK2, NfL, GFAP	LRRK2 may inform a kinase/lysosomal-pathway hypothesis, but total LRRK2 abundance is not the same as kinase activity.
Longitudinal neurodegeneration	Hypothesis-specific pathology marker plus NfL and/or GFAP	Cytokines, exploratory proteins	Repeated measurement can separate pathology-associated markers from downstream injury/response trajectories, provided the same analytical method and preanalytical workflow are maintained.
Cross-disease exploratory cohort	NfL, GFAP plus disease-relevant pathology markers	TDP-43, LRRK2, cytokines	Multiplexing is valuable for shared biological pathways, but missing disease-specific targets still require additional assays.

Brain-derived pTau217 and pTau181: biological specificity is not the same as analytical sensitivity

Brain-derived tau assays address a specific problem in blood biomarker research: circulating tau can originate from more than the CNS.

Work beginning with brain-derived total tau showed that assay designs can preferentially target short tau isoforms characteristic of CNS-derived tau rather than longer peripheral “big tau” isoforms. A 2023 primary study introduced this brain-derived tau concept as a way to improve the relationship between circulating tau and Alzheimer’s-type neurodegeneration, followed by 2024 data linking plasma brain-derived tau to amyloid-associated neurodegeneration. [9, 10]

The same idea is now being applied to phosphorylated tau species.

What does “brain-derived pTau217” actually mean?

Conceptually, a conventional pTau217 assay measures an antibody-defined population of tau carrying phosphorylation at residue 217. A brain-derived pTau217 assay adds molecular selectivity intended to enrich the measurement for CNS-origin tau species, reducing signal from relevant peripheral tau populations. The precise implementation depends on the assay’s capture/detection antibodies and epitope architecture.

That is a claim about what molecular population is targeted, not automatically about the smallest concentration that can be measured.

Consider the current MSD manufacturer specifications:

MSD S-PLEX analyte	LLOD	LLOQ	ULOQ	What this demonstrates
Conventional Tau pT217	0.880 pg/mL	5.9 pg/mL	2,400 pg/mL	Baseline conventional pTau217 analytical specification
Brain-derived Tau pT217	0.454 pg/mL	9.4 pg/mL	2,240 pg/mL	Lower LLOD than conventional pTau217, but higher LLOQ
Brain-derived Tau pT181	0.209 pg/mL	2.9 pg/mL	1,260 pg/mL	Different analytical profile again

Research-use-only (RUO) testing through Eve Technologies

For researchers who want to outsource targeted neurodegeneration biomarker testing, Eve Technologies currently offers several complementary MSD-based options: the early access Neurodegeneration 7-Plex, Neurology 3-Plex, Brain-Derived pTau217, Brain-Derived pTau181, conventional pTau217 and high-sensitivity cytokine testing within its MSD Discovery Assay portfolio.

The most appropriate option depends on the biological endpoint, species, matrix, expected biomarker concentration, required comparability with previous work and available sample volume. Researchers planning low-volume, unusual-matrix or multi-platform projects should confirm current specifications with us before finalizing sample allocation.

Frequently Asked Questions

1. What is the most useful biomarker for neurodegeneration?

There is no universal “best” biomarker because biomarkers answer different questions. NfL is useful for neuroaxonal injury and progression but is not disease-specific; p-tau217 is strongly associated with Alzheimer’s pathology; α-synuclein seed amplification assays identify synuclein biology; and emerging TDP-43 approaches aim to identify TDP-43 proteinopathy. Multimarker designs are increasingly used when both pathology and downstream injury need to be characterized.

2. Is plasma replacing CSF in neurodegeneration research?

Not universally. Plasma is more scalable and suitable for repeated collection, and some Alzheimer’s plasma assays now perform extremely well. CSF remains closer to CNS biology and is particularly important for biomarkers such as α-synuclein SAA. Imaging and CSF also remain valuable as reference standards when validating blood assays.

3. Why combine NfL and GFAP?

NfL primarily reflects neuroaxonal injury, whereas GFAP is associated with astrocytic activation. Measuring them together can provide complementary information about neuronal damage and glial response, but neither alone identifies the molecular cause of a neurodegenerative disorder.

4. Why is TDP-43 an important biomarker target?

TDP-43 pathology is central to most ALS and many forms of FTLD, but accessible pathology-specific biomarkers have historically been lacking. Plasma extracellular-vesicle approaches reported in 2024 showed encouraging discrimination of TDP-43-associated pathology, although broader independent validation is still needed.

5. Are Eve Technologies’ neurodegeneration assays diagnostic tests?

No. The Early Access Human MSD® Neurodegeneration 7-Plex and all related Discovery Assays are offered for research use only, not as clinical diagnostic tests.

6. When does a pay-per-well approach make sense?

It can be useful for pilot work, limited sample cohorts or targeted validation where purchasing and running a complete plate is unnecessary. Our Discovery Assays can be purchased in single reaction wells and do not require researchers to purchase a full assay plate. 

References:

1. Jack, C.R. Jr., Andrews, J.S., Beach, T.G. et al. Revised criteria for diagnosis and staging of Alzheimer’s disease: Alzheimer’s Association Workgroup. Alzheimers Dement 20, 5143–5169 (2024). https://doi.org/10.1002/alz.13859
2. Park, M.-K., Ahn, J., Lim, J.-M. et al. Prediction of cognitive decline and Alzheimer’s disease conversion by a plasma biomarker panel in non-demented individuals. Geroscience 48, 3921–3937 (2026). https://doi.org/10.1007/s11357-025-01869-2
3. Palmqvist, S., Warmenhoven, N., Anastasi, F. et al. Plasma phospho-tau217 for Alzheimer’s disease diagnosis in primary and secondary care using a fully automated platform. Nat Med 31, 2036–2043 (2025). https://doi.org/10.1038/s41591-025-03622-w
4. Jiang, Y., Zheng, W., Xia, Z. et al. Head-to-head comparison of brain-derived pTau217 and total pTau217 for brain amyloid and tau pathology classification. Proc Natl Acad Sci USA 123, e2536792123 (2026). https://doi.org/10.1073/pnas.2536792123
5. Giacomucci, G., Tabbì, S.M.R., Ingannato, A. et al. Refining Alzheimer’s disease biological diagnosis with plasma biomarkers: Resolving p-tau217 “gray zone” with p-tau181 integration. Alzheimers Dement (Amst) 18, e70285 (2026). https://doi.org/10.1002/dad2.70285
6. Kang, H., Woo, S.-Y., Shin, D. et al. Reproducibility of plasma biomarker measurements across laboratories: Insights into ptau217, GFAP, and NfL. Dement Neurocogn Disord 24, 91–101 (2025). https://doi.org/10.12779/dnd.2025.24.2.91
7. Guillén, N., Esteller, D., Sarto, J. et al. Plasma p-Tau217 and GFAP predict widespread cognitive decline in Alzheimer’s disease. J Neurol 273, 28 (2025). https://doi.org/10.1007/s00415-025-13556-5
8. Roveta, F., Bonino, L., Piella, E.M. et al. Neuroinflammatory biomarkers in Alzheimer’s disease: From pathophysiology to clinical implications. Int J Mol Sci 25, 11941 (2024). https://doi.org/10.3390/ijms252211941
9. Gonzalez-Ortiz, F., Turton, M., Kac, P.R. et al. Brain-derived tau: a novel blood-based biomarker for Alzheimer’s disease-type neurodegeneration. Brain 146, 1152–1165 (2023). https://doi.org/10.1093/brain/awac407
10. Gonzalez-Ortiz, F., Kirsebom, B.-E., Contador, J. et al. Plasma brain-derived tau is an amyloid-associated neurodegeneration biomarker in Alzheimer’s disease. Nat Commun 15, 2908 (2024). https://doi.org/10.1038/s41467-024-47286-5