Cover Story: In Search of MS Biomarkers

In Search of MS Biomarkers

By Tom Garry
Edited by Susan Wells Courtney
Reviewed by Barry A. Hendin, MD

Introduction

Think of multiple sclerosis (MS) as a jigsaw puzzle.

Most of us start a jigsaw puzzle with the smooth-edged border pieces that fit together easily to provide a framework for the entire puzzle. With this image in mind, we can think of the more pronounced signs and indications of MS – such as symptoms, neurological exam findings, and lesions seen on magnetic resonance imaging (MRI) – as those smooth-edged border pieces that fit together easily to provide a framework for viewing the disease.

Once the border pieces are in place, now comes the more challenging part of the puzzle, where we need to find exact locations for all of those inside pieces. The same is currently true for researchers and clinicians as they seek a fuller picture of MS. Similar to a jigsaw puzzle, they must decide whether and where several additional puzzle pieces belong within that framework.

Those puzzle pieces are biomarkers. Identifiable on imaging (MRI) or measurable in the blood or cerebrospinal fluid (CSF), they have the potential to greatly enhance the diagnosis, treatment, and ongoing management of MS. Properly understood and utilized, they can provide laboratory scientists with critical guidance in developing new medications, help clinicians develop highly individualized treatment plans, and enable people with MS to make key decisions about their care.

This article will examine both emerging biomarkers and the expanding capabilities of established ones. It will look at the science supporting their role in managing MS and the considerable promise they hold. However, it is also important to understand the limitations of these measures, so a brief accompanying sidebar provides perspective on that topic. Please see MS Biomarkers: Three Caveats to Bear in Mind for details.

SEE ALSO:

MS Biomarkers: Three Caveats to Bear in Mind

Serum NfL Testing Information

Emerging and Established Biomarkers

Our guide to this fascinating, sometimes complex subject, is a neurologist and MS specialist in Phoenix, Arizona, MSAA’s Chief Medical Officer Barry Hendin, MD. In a recent interview, Dr. Hendin began his discussion of the topic with a definition.

“A biomarker is something we can measure that gives us meaningful information about the patient’s health, such as the presence of a disease, the way that condition is responding to treatment, or the progression of the condition over time,” Dr. Hendin explains. He adds, “In MS, biomarkers can be divided into two categories. The first consists of imaging or radiological biomarkers, most notably various characteristics identified on MRI. The second consists of humoral biomarkers, with ‘humoral’ referring to bodily fluids, often relating to antibodies and immune responses. These include substances found in the blood or cerebrospinal fluid.”

Dr. Hendin notes that as imaging technology has become more powerful and laboratory techniques more sophisticated, recent years have seen the emergence of intriguing new potential biomarkers as well as a heightened ability to derive insights from existing ones.

“In MS and in all of medicine, a major focus over the last decade has been to provide individualized care. This means tailoring our treatment plans to the specifics of a patient’s condition. The information that biomarkers provide, when evaluated in the context of a person’s overall health and in conjunction with other findings, can be immensely helpful in this effort,” Dr. Hendin says.

Start at the Beginning, with Diagnosing MS

Multiple sclerosis can be very difficult to diagnose. In eight recent studies that examined the records of patients treated at specialty clinics, between 5% and 18% of people diagnosed with MS were found to actually have other conditions. The challenges of correctly identifying MS arise largely from how many other conditions can mimic the disease. The long list of imitators includes other neurologic conditions, vascular diseases, psychiatric disorders, and several autoimmune diseases.

Two conditions that can be particularly difficult to distinguish from multiple sclerosis are fellow autoimmune diseases that, like MS, are marked by demyelination of nerve sheaths (the myelin covering of a nerve): neuromyelitis optica spectrum disorders (NMOSD) and myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD). Because NMOSD and MOGAD cause demyelination just as MS does, people with these rare conditions can have symptoms and MRI findings that can easily be attributed to multiple sclerosis.1

Given this potential for misrecognition, Dr. Hendin says that two of the most important biomarkers in assessing a patient for potential MS serve to rule out multiple sclerosis rather than to support its diagnosis.

He explains, “Aquaporin-4, or AQP4, is a protein found in the brain that helps regulate water balance in the central nervous system and movement across the blood-brain barrier. NMOSD is an autoimmune disease, a condition in which the immune system mistakenly identifies a normal substance in the body as a threat and produces antibodies to attack it.

“In NMOSD, aquaporin-4 is the target and the antibodies acting against it are known as AQP4-IgG. These antibodies are found in the blood of most people with NMOSD, and blood tests showing their presence are key to excluding the possibility of MS and diagnosing NMOSD instead.” Dr. Hendin adds that distinguishing between the two conditions is critical because they are treated with different types of medications, with MS therapies typically not being effective against NMOSD and some older multiple sclerosis medications actually having the potential to make the condition worse.2

Similarly, Dr. Hendin notes, in MOGAD, the immune system targets myelin oligodendrocyte glycoprotein (MOG). This protein is found on the surface of oligodendrocytes, the cells that produce myelin (myelin is the fatty substance that coats the nerve fibers at the end of neurons to facilitate efficient transmission of electrical signals). MOG is also found on the surface of the myelin sheath itself, and in MOGAD, autoantibodies attack the protein in both locations. The presence of those antibodies, known as MOG-IgG, in the blood or CSF, shifts a clinician’s focus from MS to MOGAD.

But what about the biomarkers that serve to confirm the diagnosis of MS rather than exclude it?

“Both radiographic and humoral (fluid) biomarkers have roles to play in identifying multiple sclerosis,” Dr. Hendin says, adding that “MRI is the best-validated biomarker in MS, both in terms of diagnosing the disease as well as monitoring and predicting its course.”

Dr. Hendin explains that the current era of MS diagnosis began in 2001, when a neurologist from New Zealand named W. Ian McDonald led an international panel of experts in developing guidelines for diagnosing MS that became known as the McDonald criteria. Those standards specified that MRI detection of brain lesions – either alone or in conjunction with clinical findings and other assessments – could justify a diagnosis of multiple sclerosis.3

The 2001 McDonald criteria also noted that the presence of oligoclonal bands, or clusters of immunoglobulin proteins in the CSF, constituted supportive evidence of MS, as did an elevated level of immunoglobulins in the CSF. Dr. Hendin explains that immuno-globulins are antibodies produced by the immune system and that oligoclonal bands can be evidence of chronic inflammation. In addition, increased levels of immunoglobulins, as identified by a measure known as the IgG index, reflect abnormal immune activity in the central nervous system.

The McDonald criteria have been revised several times to incorporate advances in imaging, laboratory science, and researchers’ overall understanding of MS. The most recent update was unveiled in September 2024 at the 40th Congress of the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS) in Copenhagen, Denmark. As with past iterations, the latest version of the McDonald criteria assigns roles to both MRI and humoral biomarkers in identifying multiple sclerosis.

“Brain and spinal cord MRI remain the most useful paraclinical test to aid the diagnosis of multiple sclerosis,” Spanish neurologist Xavier Montalban, MD, said in presenting the 2024 updates. Dr. Montalban, who chaired the international committee of 55 experts who developed the updated criteria, added, “An abnormal MRI showing typical lesions is required to make the diagnosis of MS.”4

MRI facilitates the identification of MS primarily by demonstrating that lesions are present in multiple areas of the central nervous system. This finding is necessary to meet the McDonald criteria’s requirement for “dissemination in space.” Prior to the 2024 update, imaging had to show lesions in at least two of four regions of the CNS. Three of those areas are in the brain, while the spinal cord is the fourth region.

Man reading MRI scansThe latest version of the McDonald criteria adds the optic nerve as a fifth region where the presence of lesions can fulfill the criterion of dissemination in space. Dr. Hendin notes that this change may facilitate timely diagnosis of MS. This is because optic neuritis, an inflammation of the optic nerve that can impair vision and cause pain behind the eye, is the first symptom experienced by one-quarter to one-third of people who are diagnosed with multiple sclerosis following an initial demyelinating event.4 (A “de-myelinating event” is when damage has occurred to the protective covering of the nerves of the CNS, as seen on an MRI.)

“This expansion of the regions that can satisfy the ‘dissemination in space’ requirement underscores the central role of MRI in identifying MS while also increasing the prominence of two other assessments – optical coherence tomography and visual evoked potentials – which the 2024 criteria included as acceptable means of demonstrating optic nerve involvement,” Dr. Hendin explains.

Dr. Hendin adds that the optical coherence tomography, or OCT, is a non-invasive procedure that uses light waves to create high-resolution images of the retina. These images and sophisticated software enable physicians to measure the thickness of different retinal layers and the optic nerve, allowing identification of nerve inflammation and swelling.

In visual evoked potential (VEP) testing, the patient sits in a chair and a technician attaches electrodes to the patient’s scalp to record brain activity. The test involves looking at a screen that displays a flashing pattern. The brain waves recorded by the electrodes provide neurologists with important information about the person’s visual pathway, which connects the eye to the brain via the optic nerve.

Dr. Hendin notes that the 2024 update also cites two relatively new MRI assessments, the central vein sign (CVS) and paramagnetic rim lesions (PRLs), as optional tools that can aid in the diagnosis of MS.

“The central vein sign refers to a small vein running through the center of a brain lesion that can be seen on certain MRI scans,” Dr. Hendin continues, adding, “The presence of a central vein indicates inflammatory demyelination characteristic of MS.” Research has shown that the CVS can help distinguish MS from other diseases, identify ongoing disease activity, and predict the likelihood of additional lesions developing.5

Turning to the other MRI biomarker new to the McDonald criteria, Dr. Hendin points out that paramagnetic rim lesions, or PRLs, are MS lesions that have a thin, dark rim encircling them on imaging. The rim is composed of iron-rich cells, which is significant because iron can contribute to neurotoxicity. “Several studies have demonstrated that a higher number of PRLs at diagnosis or shortly thereafter is associated with an increased risk for disability progression and brain atrophy in the future,” Dr. Hendin says.6

Another feature of the 2024 update is the proviso (or condition) that proteins known as kappa free light chains, or kFLC, have diagnostic properties similar to oligoclonal bands (OCBs) and that identifying elevated levels of kFLCs in the cerebrospinal fluid can substitute for assessing OCBs when evaluating potential MS.4 Dr. Hendin explains that above-normal amounts of kFLC can be produced when there is chronic inflammation in the fluid-filled intrathecal space between the layers of tissue that cover the brain and spinal cord.

SIDEBAR:

MS Biomarkers: Three Caveats to Bear in Mind

While introducing the latest version of the McDonald criteria, Dr. Montalban stressed that MS remains a diagnosis of exclusion, meaning that other conditions must be ruled out before determining that a person has multiple sclerosis.4 Dr. Hendin says, “Because MS has many presenting features that overlap with other conditions, the ability to consider a variety of imaging findings and laboratory test results is incredibly helpful in eliminating one or another alternative explanation for a patient’s symptoms and assembling an array of evidence in which all or most of the information points to multiple sclerosis.”

Formulating the Initial Treatment Plan

“Both imaging and humoral biomarkers continue to play an important role following diagnosis,” according to Dr. Hendin. He also notes that with more than 20 disease-modifying therapies (DMTs) approved by the Food and Drug Administration to treat MS, clinicians and patients have numerous options for selecting an initial therapy. One of the key decisions in selecting that first medication, he adds, is whether to start with a therapy considered a “high-efficacy” DMT or a “moderate-efficacy” DMT.

Doctor and patient reviewing a plan width=

Shared decision-making is the concept of patients and their healthcare team sharing information and working together. Biomarker results can make an important contribution to this decision-making process.

Dr. Hendin explains that physicians in all fields of medicine try to prescribe therapies that are likely to offer patients meaningful benefit while limiting the potential for side effects. Because more potent medicines are often associated with more significant side effects, physicians often take a “start low, go slow” approach. In other words, they try to find the lowest dose of a medication or least-potent choice of medication that will be effective for a patient, proceeding to higher doses or higher-potency therapies only if needed.

However, the use of that approach in MS has been challenged recently by a number of studies showing that beginning treatment with a high-efficacy DMT offers many people better long-term outcomes than starting with a moderate-efficacy medication. For example, in a study of 694 people with MS in Norway, 68% of people who took a high-efficacy medication as their first DMT had no evidence of disease activity (NEDA) one year later, compared to 36% of people who started a moderate-efficacy therapy.7 The results of that and other studies prompted a panel of experts to advise, “Early intervention with high-efficacy disease-modifying therapies may represent the best window of opportunity to delay irreversible central nervous system damage and MS-related disability progression.”8

Dr. Hendin says that based on such research, and the fact that further progress needs to be made in using biomarkers and other means to better predict each person’s MS course, early use of high-efficacy therapies remains appropriate for most patients. At the same time, he adds, biomarker results can help inform the shared decision-making process between individuals with MS and their clinician. “The ultimate decision about selecting a DMT should come from this process,” he says, explaining that when biomarker findings and the patient’s clinical course are favorable, some patients may choose high-efficacy therapies while others may prefer to select from a broader range of treatment options.

“A number of MRI features can inform the patient’s prognosis or outlook,” Dr. Hendin states. He adds that these include the location of lesions, the presence of paramagnetic rims around lesions, and gadolinium enhancement, among others. He explains that gadolinium is a contrast agent that is injected into a person’s veins before an MRI. A white “enhanced” region on the MRI following gadolinium injection indicates an active lesion with inflammatory activity.

“MRI findings that show current inflammatory activity or that are associated with greater disability over time are important factors to weigh when a person considers the potential benefits and risks of initiating treatment with a high-efficacy therapy,” Dr. Hendin notes.

Meanwhile, neurofilament light chain, or NfL, is a relatively new fluid biomarker that can also aid in determining prognosis. Dr. Hendin explains that neurofilaments are proteins found in neurons. When there is damage to the axons (the projections at the end of nerve cells that transmit electrical impulses), NfL is released into the CSF and blood. Because NfL can be released in response to neuronal damage resulting from many causes, including degenerative neurological diseases and brain trauma, elevated levels of the protein are not one of the key biomarkers neurologists use in diagnosing MS.9

However, once multiple sclerosis has been diagnosed, baseline NfL levels have been shown to provide important clues about disease severity and outlook. Higher serum levels of NfL are associated with an elevated risk for increased disability and for developing new lesions and gadolinium-enhancing lesions in the following year. As will be discussed later, NfL levels can also help confirm relapses, track disease progression, and assess response to therapy.9

Another serum biomarker can provide critical risk-benefit information for people who are thinking about starting certain high-efficacy DMTs. The biomarker tests for antibodies to the John Cunningham virus, or JCV. Dr. Hendin points out that this virus does not cause symptoms and is usually kept in check by the immune system. However, when the immune system is unable to control the virus, JCV can cause a potentially fatal inflammatory disease called progressive multifocal leukoencephalopathy, or PML.

Because certain high-efficacy DMTs can suppress the immune system in ways that may increase the risk for PML, neurologists generally advise patients who have JCV antibodies to start treatment with other therapies. If those medications do not reduce relapses or slow disease progression, the high-efficacy DMTs associated with risk for PML in JCV antibody-positive patients are not absolutely contraindicated, but clinicians typically would use them with caution. (When “contraindicated,” a specific medication should not be used.)

Ongoing Monitoring and Decision-Making

A single MRI or blood test can provide a useful snapshot of a person’s health at any given moment. But much of the value of biomarkers lies in their ability to track measures of MS over time, more in keeping with a video than a snapshot.

Dr. Hendin explains that ongoing monitoring is one area where assessing humoral biomarkers eventually may prove particularly helpful. He adds, however, that there is not yet sufficient evidence to support routinely measuring fluid-based biomarkers at specific intervals.

An international panel of experts working in conjunction with the Consortium of Multiple Sclerosis Centers (CMSC) last year issued guidelines that recommended measuring serum NfL levels in specific circumstances, such as three-to-six months after a relapse or after MRI results showing gadolinium-enhancing lesions. The experts also advised re-measuring NfL if new or enlarging lesions are found on MRI.9

The international panel further recommended that blood levels of NfL be measured every three-to-six months to evaluate the effectiveness of a DMT in people with no evident MRI changes or no clinical changes. The experts added, “If NfL levels have not decreased (or are found to increase) within six months of initiating DMT, consideration should be made for changing the therapy or escalating to a higher-efficacy DMT.” 9

Dr. Hendin says that measuring fluid biomarkers such as NfL and by MRI may also help with early detection of progression independent of relapse, or PIRA. He explains, “PIRA describes an insidious [gradual and subtly harmful] situation in which people with MS experience increased disability and an overall worsening of their condition without having a relapse. We know that relapses tend to decline with age, as the inflammatory activity of MS generally diminishes over time. However, that does not mean that the disease is not continuing to progress in a gradual fashion.”

SIDEBAR:

Serum NfL Testing Information

In combination with assessments of a patient’s physical and cognitive function, identifying unfavorable changes on MRI or in fluid biomarkers can help clinicians and patients decide whether to switch DMTs, begin physical or occupational therapy, introduce a mobility aid sooner rather than later, or take other steps.

Biomarkers may also play an increasing role in helping clinicians and patients address one of the most-controversial questions in MS today: whether older people who have not experienced a relapse or had marked disease progression over several years on a DMT should discontinue therapy.

“This is a very challenging issue because arguments can be made both for and against stopping treatment,” Dr. Hendin states. He explains that as people age, they tend to acquire other health conditions, such as high blood pressure, diabetes, or obesity, which may increase their susceptibility to medication side effects and interactions between medications. The cumulative burden of those conditions can also detract from overall health, increasing the impact of side effects.

If a person’s MS apparently has been stable for many years, the potential for increased harm from side effects may tilt the risk-benefit calculation in favor of stopping a DMT. On the other hand, Dr. Hendin notes, evidence has shown that progression independent of a relapse is a very real phenomenon. Further, clinical studies of discontinuing DMTs in older people who have been stable on therapy have yielded mixed findings, with one major trial having inconclusive results10 and a 2025 study showing that roughly 20% of people who discontinue their first-line DMT will have a recurrence of disease activity.11

“While this issue continues to be examined on a large scale in clinical trials, individual patients and their clinicians have to look at what makes sense for different people given their specific situation,” Dr. Hendin says. He adds that although biomarkers may help augment clinical assessment in weighing whether to stop or continue treatment, their role in this decision-making process has not been clearly defined.

Other Biomarkers in Use and on the Horizon

SIDEBAR:

Emerging and Established Biomarkers

Several other biomarkers have entered clinical use recently or are in late stages of evaluation. For example, the Octave® Multiple Sclerosis Disease Activity (MDSA) Test examines 18 biomarkers to assess the likelihood and severity of disease activity. 12 Researchers are also studying a number of individual fluid markers, including:

  • Glial fibrillary acidic protein (GFAP), a filament in astrocytes, the central nervous system (CNS) cells that support neurons. Following a brain injury, GFAP is released into the cerebrospinal fluid (CSF) and blood.13
  • Chemokine (C-X-Cmotif) ligand13 (CXCL13), a small protein that acts as a signaling molecule to attract B cells to the CNS.13
  • Chitinase 1 (CHIT1), a marker of inflammation in the microglia, immune cells that monitor the CNS for signs of damage or harmful substances.13
  • Chitinase-3-like protein 1 (CHI3L1), which is expressed by CNS cells and is a marker of microglial activation and ongoing damage.13

Numerous MRI measures can also be assessed, including those looking at enlargement of existing lesions, total brain volume, and the volume of functional (referred to as “parenchymal”) tissue in the brain. While some, such as evidence that a previously identified lesion is becoming larger, are important to clinicians in their decision-making, others are more relevant for research purposes.

Dr. Hendin concludes, “As the number of biomarkers has expanded in step with the number of disease-modifying therapies, people with MS and their clinicians have a greater ability than ever to develop a treatment plan that reflects the person’s unique situation and offers the best outcomes for that individual. This is a wonderful development and reason to look to the future with a strong sense of hope and optimism.”

References

  1. Rjeily NB, Solomon A. Misdiagnosis of multiple sclerosis: past, present, and future. Curr Neurol Neurosci Rep. 2024;24:547-557.
  2. Mader S, Brimberg L. Aquaporin-4 water chanel in the brain and its implications for health and disease. Cells. 2019;8:90; doi:10.3390/cells8020090.
  3. McDonald WI, Compston A, Edan G, et al. Recommended diagnostic criteria for multiple sclerosis: guidelines from the International Panel on the Diagnosis of Multiple Sclerosis. Ann Neurol. 2001;50:121-127.
  4. Montalban X for the International Advisory Committee on Clinical Trials in Multiple Sclerosis. 2024 Revisions of the McDonald Criteria. 40th Congress of the European Committee for Treatment and Research in Multiple Sclerosis, Sept. 18-20, 2024. Copenhagen, Denmark. Presentation available at https://ectrims.eu/mcdonald-diagnostic-criteria. Accessed August 5, 2025.
  5. Sati S, Oh J, Constable TR, et al. The central vein sign and its clinical evaluation for the diagnosis of multiple sclerosis: a consensus statement from the North American Imaging in Multiple Sclerosis Cooperative. Nat Rev Neurol. 2016. doi:10.1038/nrneurol.2016.166.
  6. Reeves JA, Bartnik A, Jakimovski D, Mohebbi M, Bergsland N, Salman F, Schweser F, Wilding G, Weinstock-Guttman B, Dwyer MG, Zivadinov R. Associations Between Paramagnetic Rim Lesion Evolution and Clinical and Radiologic Disease Progression in Persons With Multiple Sclerosis. Neurology. 2024 Nov 26;103(10):e210004. doi: 10.1212/WNL.0000000000210004.
  7. Simonsen CS, Flemmen HO, Broch L, et al. Early high efficacy treatment in multiple sclerosis is the best predictor of future disease activity over 1 and 2 years in a Norwegian population-based registry. Front Neurol. 2021 Jun 17;12:693017. doi: 10.3389/fneur.2021.693017.
  8. Filippi M, Amato MP, Centonze D, et al. Early use of high-efficacy disease-modifying therapies makes the difference in people with MS: an expert opinion. J Neurol. 2022;269:5382-5394.
  9. Freedman MS, Gnanapavan S, et al. on behalf of the Consortium of Multiple Sclerosis Centers. Guidance for use of neurofilament light chain as a cerebrospinal fluid and blood biomarker in multiple sclerosis management. eBioMedicine. 2024;101:104970.
  10. Corboy JR, Fox RJ, Kister I, et al. Risk of new disease activity in patients with multiple sclerosis who continue or discontinue disease-modifying therapies (DISCOMS): a multicentre, randomised, single-blind, phase 4, non-inferiority trial. Lancet Neurol. 2023;22(7):568-577.
  11. Coerver EME, Fung WH, deBeukelaar J, et al. Discontinuation of first-line disease-modifying therapy in patients with stable multiple sclerosis The DOT-MS Randomized Clinical Trial. JAMA Neurol. 2025;82(2):123-131.
  12. Octave Bioscience. The Octave® MSDA Test. Available at https://www.octavebio.com/providers/. Accessed August 25, 2025.
  13. Di Filippo M, Gaetani L, Centonze D, et al. Fluid biomarkers in multiple sclerosis: from current to future applications. The Lancet Regional Health – Europe. 2024;44: 101009.

Additional References

  • Al-Louzi O, Letchuman V, Manukyan S, et al. Central vein sign profile of newly developing lesions in multiple sclerosis. Neurol Neuroimmunol Neuroinflamm. 2022;9:e1120. doi:10.1212/NXI.0000000000001120.
  • Ferreira-Atuesta C, Reyes S, Giovanonni G, Gnanapavan S. The evolution of neurofilament light chain in multiple sclerosis. Front Neuroscience. 2021;15:642384.
  • Holmoy T. The discovery of oligoclonal band: a 50-year anniversary. Eur Neurol. 2009;62:311-315.
  • Paul A, Comabella C, Gandhi R. Biomarkers in multiple sclerosis. Cold Spring Harb Perspect Med. 2019;9:a029058.
  • Thakor KA, Kaisey M. Fluid biomarkers in multiple sclerosis. Pract Neurol. 2025;7:52-55.
  • Yang J, Hamade M, Wu Q, et al. Current and future biomarkers in multiple sclerosis. Int J Mol Sci. 2022, 23, 5877. https://doi.org/10.3390/ijms23115877.

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Last Updated: October 20, 2025