ALS Biomarkers: Are We Closer to Early Detection?
"A deep dive into the cerebrospinal fluid and blood biomarkers that may revolutionize amyotrophic lateral sclerosis diagnosis and management."
Amyotrophic lateral sclerosis (ALS), a progressive and debilitating neurodegenerative disease, poses a significant challenge to healthcare. Affecting individuals typically within a few years of symptom onset, ALS lacks a cure, and its underlying mechanisms remain poorly understood. The pressing need for validated biomarkers has driven research to improve early diagnosis and disease management.
Biomarkers, objectively measured indicators of pathological processes, are critical for tracking disease progression and gauging treatment response. Body fluids, especially cerebrospinal fluid (CSF) and blood, are prime targets for biomarker discovery. CSF's direct interaction with the central nervous system makes it highly sensitive to neurological changes, while blood samples offer an accessible alternative, albeit with potentially lower sensitivity.
Recent systematic review and meta-analysis focuses on eleven frequently studied biomarkers in ALS, assessing their concentrations in CSF and blood of diagnosed patients compared to controls. By evaluating these biomarkers, researchers aim to identify potential diagnostic and prognostic tools, moving closer to personalized strategies for combating ALS.
Counting People with ALS and Tracking the Earliest Stages
The CDC's National ALS Registry explains prevalence as the proportion of people with a disease during a given time period, and notes that calendar year 2018 is the most current prevalence data available at this time. The Registry also invites people living with ALS to join to be counted and to participate in research, and it serves as a platform connecting patients with clinicians and researchers. The ALL ALS Consortium complements that effort with two studies: the ALL ALS PREVENT study aims to understand the earliest stages of the disease in people at risk, while the ASSESS ALL ALS study collects data on individuals living with ALS to track disease progression and identify new biomarkers. Meanwhile, longitudinal research assessed the association and discriminative performance of serum biomarkers with clinical disease progression and survival in patients with ALS.
How ALS Biomarkers Are Defined and Categorized
Biological markers, or biomarkers, are measurable variables that signal a normal, natural process, the presence of a disease state, or the pharmacologic response to therapy, and they can be molecular, radiographic, or physiological markers. A Nature Reviews Neurology overview describes the emerging landscape of diagnostic, categorical, and pharmacodynamic biomarkers for ALS and considers their role in the rapidly changing therapeutic landscape. A systematic review in Frontiers in Neuroscience highlights how biomarkers can be applied in clinical trials to accelerate therapeutic development and enhance patient care. Yet fluid biomarker work remains constrained by limitations: a review of fluid biomarkers notes that CSF and blood candidates are promising but face unresolved measurement and validation hurdles, and it highlights TDP-43—a protein intimately involved in ALS pathogenesis—as a key target still being tested for reliability as a biomarker.
From Charcot to Natural History Cohorts
ALS, also known as motor neuron disease (MND), Lou Gehrig's disease, or Charcot's disease, is a rare terminal neurodegenerative disease defined by the progressive loss of both upper and lower motor neurons that normally control voluntary muscle contraction. Current knowledge of the natural history of ALS derives largely from regional and national registries with broad representation, and the ALS National History Cohort (NHC) found its participants had a higher diversity of diagnostic and demographic data compared to ALS clinical trial participants. A 2025 analysis of a large, well-defined, population-based European cohort mapped time to key clinical milestones in ALS, highlighting the phenotypic and genetic factors affecting the heterogeneous disease course. The authors concluded that the analysis provides detailed insight into the natural history of ALS and can help guide clinical care and stratify individuals to assess therapeutics in clinical trials.
Decoding ALS with Fluid Biomarkers: What the Research Reveals
Researchers conducted a comprehensive analysis of existing studies to evaluate the potential of specific biomarkers in diagnosing and understanding ALS. The study followed rigorous guidelines (PRISMA-P) to ensure a systematic and unbiased approach. They looked at observational studies that measured the levels of certain substances in the cerebrospinal fluid (CSF) and blood of ALS patients and compared them to those without the condition.
- Amyloid beta (Aβ-42)
- Tau and phosphorylated tau (p-Tau)
- Neurofilaments
- S100β
- Cystatin C
- Progranulin (PGRN)
- Glial fibrillary acidic protein (GFAP)
- Monocyte chemoattractant protein-1 (MCP-1)
- Brain-derived neurotrophic factor (BDNF)
- TAR DNA-binding protein-43 (TDP43)
- YKL-40
- Chitotriosidase (CHIT1)
Fluid Biomarkers Across CSF, Blood, Urine, Saliva, and Tears
A recent review offers a critical appraisal of fluid-based biomarkers for ALS across multiple sources—cerebrospinal fluid (CSF), blood, urine, saliva, and tears—with emphasis on their diagnostic and prognostic potential. The review weighs both the promise and the limitations of each biofluid, and it assesses how ready these candidates are for clinical translation. The same review is indexed among the latest coverage on the Nature Reviews Neurology subjects page, which also features work describing the emerging landscape of diagnostic, categorical, and pharmacodynamic biomarkers for ALS. Together these reviews signal that the field is moving from single-marker studies toward a broader search for reliable, reproducible fluid-based signals.
The Obstacles: Proteinopathy Discordance and Biological Heterogeneity
Despite decades of progress, ALS biomarker discovery has repeatedly run into obstacles. The discovery of biomarkers that are specific to ALS pathology has focused on the study of TDP-43 as a disease-associated proteinopathy, since in ALS and frontotemporal dementia (FTD), TDP-43 is mislocalized from the nucleus to the cytoplasm. Even with advances in understanding the genetic basis of the disease—particularly mutations in Chromosome 9 Open Reading Frame 72 (C9orf72), superoxide dismutase 1 (SOD1), and TAR DNA-binding protein—researchers note that ALS remains a fatal neurodegenerative disease characterized by the progressive loss of upper and lower motor neurons, leading to muscle weakness, paralysis, and ultimately respiratory failure. These sources underscore that genetic insight has not yet translated into a pathologically specific biomarker, and that the disease's heterogeneity continues to complicate early and reliable detection.
What a Biomarker Is—and What ALS Needs It to Do
The ALS Association defines biomarkers (short for biological markers) as genes, proteins, or other substances or characteristics that health care professionals can test for or measure. They can be found in blood, cerebrospinal fluid (CSF), other body fluids, or tissues, and they are extremely important for diagnosing and managing a wide range of diseases. In the ALS context, the critical question is whether candidate markers can move beyond general signals of neurodegeneration toward disease-specific, early-stage detection that informs diagnosis, prognosis, and treatment monitoring.
The Future of ALS Treatment: Biomarkers as Guiding Lights
This systematic review and meta-analysis is a crucial step toward understanding the complex landscape of ALS biomarkers. By synthesizing existing research, the study aims to pinpoint reliable markers that can differentiate ALS patients from healthy individuals. Furthermore, it seeks to uncover how these biomarkers relate to the clinical characteristics of the disease, paving the way for personalized treatment strategies.
The Consensus: Neurofilaments Lead, Reproducibility Lags
Expert reviews converge on neurofilaments as the strongest current biomarker signal in ALS, while also flagging reproducibility as a persistent technical challenge. A Frontiers in Molecular Biosciences review summarizes recent developments focusing on neurofilaments in each biofluid, transcriptomic signatures, and neuroinflammatory biomarkers, and it emphasizes the technical challenges surrounding reproducibility in measurement. A separate MDPI review takes a pathophysiologic approach to summarizing clinical studies using quantitative biofluid biomarkers in ALS, discusses the utility and shortcomings of each biomarker, and highlights the superiority of neurofilaments as biomarkers of neurodegeneration over other candidate biomarkers. Read together, these syntheses suggest neurofilaments are the closest thing ALS research has to a workhorse marker—but not yet a definitive, stand-alone diagnostic tool.
Multi-Omics and the Rise of NfL
Recent advancements in multi-omics technologies have significantly transformed the identification of potential biomarkers and therapeutic targets for ALS. Notably, neurofilament light chain (NfL) levels in cerebrospinal fluid and blood have emerged as promising indicators for early diagnosis and monitoring disease progression. Global research trends point toward integrating these multi-omics approaches with fluid biomarkers to accelerate the path to an early-detection test. This outlook positions NfL as the leading near-term candidate while multi-omics discovery continues to expand the pipeline of new markers.
The Delivery Problem Is Larger Than the Science
Beyond the lab, ALS biomarker research faces systemic challenges that no single assay can fix. Because ALS is rare and heterogeneous, progress depends on sustained collaboration across institutions, consistent standards for sample collection and measurement, and data sharing that spans registries, clinical trials, and natural history cohorts. Widely understood bottlenecks include slow enrollment, fragmented data, and the gap between promising research findings and validated tests available to clinicians, meaning breakthroughs in biomarker discovery will only matter if the surrounding infrastructure is built to translate them into routine care.
From Consortium Data to a DoD-Funded Proteomics Hunt
Real-world impact increasingly depends on pooling patient data and biospecimens that are otherwise scattered across multiple institutions. The causes of ALS involve a range of genetic, environmental, and lifestyle factors, resulting in considerable differences in how the disease initiates, progresses, and responds to treatment, and researchers note that decentralized data make it challenging to identify common biomarkers—motivating public–private partnerships to consolidate resources. The ALS/MND Natural History consortium, comprising nine ALS clinics, collects real-world data on patients with ALS/MND, including medical history, medication, longitudinal outcomes, survival, and demographics, and applied propensity score matching (PSM) to create a dataset balanced on factors associated with ALS survival. On the funding side, in 2022 ALS TDI received a $281,000 grant from the Department of Defense to conduct an unprecedented proteomics study in blood samples provided by participants in the ALS Research Collaborative (ARC) study, aiming to find potential blood-based biomarkers for ALS.
The identification of robust biomarkers holds immense potential for improving ALS diagnosis and management. Early detection could allow for timely interventions, potentially slowing disease progression and improving quality of life. Biomarkers could also aid in patient stratification, ensuring that individuals receive the most appropriate and effective therapies based on their unique disease profiles.
Ultimately, this research strives to guide future investigations, fostering the development of targeted therapies and diagnostic tools that can transform the lives of those affected by ALS. The search for reliable biomarkers represents a beacon of hope in the fight against this devastating condition.