How Blood-Based NfL Testing Could Transform Multiple Sclerosis Management

Elecsys NfL is a CE-marked blood test designed to help identify neuroinflammation in adults with RRMS. Intended for use alongside other clinical, imaging, and laboratory evaluations, the assay measures NfL protein—a marker of neuroaxonal injury and neurodegeneration characteristic of MS.

Regular MRI monitoring is a cornerstone of modern MS management; however, it only detects damage after it has occurred and is performed at intervals between 3 and 24 months, depending on individual patient factors such as disease stability.

Complementing MRI imaging, the NfL blood test represents a significant step forward in the management of the disease, enabling clinicians to detect real-time axonal damage frequently and conveniently through a simple blood draw. 

The unmet clinical need is substantial. As of 2023, 2.9 million people were living with MS—a significant >26% increase from 2.3 million only 10 years previously in 2013.  What makes this trend particularly concerning is that people with all forms of MS experience disease progression from the outset. Delays in diagnosis and treatment can have far-reaching consequences, negatively impacting both physical and mental health while creating a substantial financial burden for individuals and society.

The central goal of MS treatment is to slow, stop, or ideally prevent progression as early as possible. For those with RRMS specifically, detecting neuroinflammation is critically important, enabling patients and their physicians to make informed decisions about disease management, potentially minimizing relapse occurrence and worsening of disability. 

Currently, MRI is the standard tool for monitoring neuroinflammation in MS. However, its cost, limited availability, and the burden it places on patients—particularly those who suffer from claustrophobia—mean that regular, frequent monitoring is not always feasible. This leaves clinicians without the timely information they need to adjust treatment and respond swiftly to disease activity. A more accessible and lower-cost option with faster turnaround times is therefore needed to support more frequent testing.

As a breakthrough in disease management, Elecsys NfL is designed to complement rather than replace existing tools, integrating into current MS workflows alongside standard clinical, imaging, and laboratory evaluations. Crucially, because it requires only 48 microliters of blood (equivalent to a single drop), it enables frequent, routine testing with a significantly faster turnaround time and greater convenience for patients than MRI.

MRI, while invaluable, is not conducive to frequent monitoring, particularly for those located far away from specialist care centers. Results can also vary depending on how the scan is performed. The type of MRI machine used, whether a contrast dye is administered to highlight active inflammation, and which part of the central nervous system is imaged, all determine what the scan reveals and what it may miss.

Elecsys NfL addresses some of these gaps by offering clinicians a complementary, blood-based source of information between imaging intervals, potentially enabling earlier detection of disease activity and more timely treatment decisions. When used in combination with clinical evaluation by physicians, the results may help provide reassurance and optimize the timing and frequency of MRI testing.

Blood-based NfL tests have been available for some time, but until now, as research use only (RUO) assays, not validated for routine clinical use. Elecsys NfL is a CE-marked, fully automated assay for NfL measurement, requiring a simple routine blood draw, and delivers results in just 18 minutes.

Running on Roche Diagnostics cobas® analyzers, which are already widely deployed across hospital laboratories worldwide, it has the potential to bring NfL testing out of the specialist research setting and into everyday clinical practice.

A further differentiator is the assay's approach to result interpretation. NfL levels naturally increase with age, rising approximately 2% to 3% annually in healthy individuals and accelerating after the age of 50. 

Other NfL assays rely either on a single, fixed numerical cut-off for all patients regardless of age, or on broad age brackets of up to ten years—both of which risk obscuring clinically meaningful differences. Elecsys NfL addresses this by using age-adjusted percentiles to compare patient results against an age-matched healthy reference group, giving clinicians the clarity needed to differentiate true disease-driven neuroinflammation from normal aging.

Neurofilaments are structural proteins exclusively located in the neuronal cytoskeleton—the internal support system that maintains the complex architecture of these cells, enabling their critical functions. When neurons are injured or undergo degeneration, neurofilaments are released into the interstitial fluid and can be detected subsequently in both cerebrospinal fluid and blood. Neurofilament concentrations have been shown to correlate with the extent of axonal damage or neurodegeneration across various diseases.

As a structural neuronal protein distributed throughout the central nervous system, NfL serves as a general indicator of neuroaxonal damage rather than a disease-specific marker. This makes accurate interpretation of results, taking into account factors such as age and comorbidities, essential. 

This is a critical practical consideration for clinicians. There is currently no single international reference standard for NfL testing, which means different manufacturers' assays use distinct antibodies and produce varying absolute numerical values.

Whilst tests like Elecsys NfL and other research assays demonstrate excellent correlation with one another and yield consistent clinical insights, their raw numbers cannot be used interchangeably.

Elecsys NfL is traceable to the National Institute of Standards and Technology (NIST), providing a level of measurement confidence not available with all platforms. For accurate longitudinal monitoring, which is essential to good clinical practice, patients' NfL levels need to be tracked using the exact same analytical platform over time. If a patient changes laboratories or healthcare settings, a new baseline measurement should be established. 

As a structural neuronal protein located across the central nervous system, NfL is an indicator of general neuroaxonal damage rather than a pathology-specific marker, meaning elevated levels are seen across multiple neurodegenerative and neurotraumatic conditions, including Alzheimer's disease, amyotrophic lateral sclerosis, traumatic brain injury, and others. 

However, Elecsys NfL is being introduced exclusively to reflect neuroinflammation in adults with RRMS. The assay's potential applications in other neurological indications remain under active clinical investigation.

The safety and effectiveness of Elecsys NfL have not been established for monitoring responses to therapies, but its potential utility in this application also remains under active clinical investigation.

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