An MS Blood Test: Is It Possible?

MRIs often miss disease activity, and lumbar punctures are invasive. A blood test that can detect nerve damage is awaiting FDA approval.

Diagnosing multiple sclerosis (MS) can be complicated, and sometimes the diagnosis takes a long time — it took me 13 years to reach an answer.

There’s no one test that can diagnose every case of MS. Doctors have relied on the McDonald criteria for diagnosis since 2001. A revision to these criteria in 2017 enables doctors to diagnose MS earlier in the disease process, allowing treatment to begin sooner.

Currently, doctors use MRI to determine if patients fulfill the McDonald criteria for MS. They look for lesions in the brain and spinal cord that occur in multiple areas and at separate times.

But this isn’t always sufficient. The neurologist who finally diagnosed me explained that I likely had tiny lesions — too small to be seen on MRI — which is why my diagnosis took so long.

If an MRI is inconclusive, doctors may order a lumbar puncture. This test, sometimes called a spinal tap, enables doctors to take a sample of cerebrospinal fluid (CSF) and test it for the presence of oligoclonal bands, which indicate inflammation in the central nervous system and may signal the presence of MS.

Lumbar puncture is more invasive than MRI, but it’s the test that ultimately gave me my answer.

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More MRI limitations

Doctors use MRI for diagnosis and to monitor the progression of disease.

Many people can safely rely on MRI to determine if their disease is stable, but some — like me — cannot.

My MRI hasn’t changed over time despite my symptoms progressing. That has made it challenging to determine whether my treatment is effective because I cannot assume an unchanged MRI is confirmation that my medication is working — I must also assess how I feel.

In addition, MRI testing is costly and often difficult to analyze.

Also, MRI cannot predict which people are at risk for worsening disability over time.

Currently, no other tests are approved to assess MS progression. But this could soon change.

Not your father’s NfL

A new blood test has the potential to transform the way we diagnose and monitor disease activity in relapsing-remitting MS over time.

The test can detect a protein called neurofilament light chain (NfL), which is released when nerve cells are damaged. This could make it much easier for doctors to diagnose MS sooner, even when lesions don’t show up on MRI.

In addition, NfL can effectively monitor disease activity and response to treatment. And it’s more cost-effective and easier to administer and interpret than MRI.

What’s more, NfL blood levels in people with MS can predict future relapses and disease progression — which up until now has not been possible. Having this information ahead of time could help doctors and patients alike when considering future plans for lifestyle or treatment.

NfL levels may also help distinguish between MS and clinically isolated syndrome (CIS) and help determine which MS subtype a person has.

There’s yet another way the NfL blood test could help those of us living with MS. Many MS disease-modifying treatments (DMTs) have potential side effects that require close monitoring. Researchers are studying ways to safely allow patients to come off their medications after a minimum of 5 years, hopefully, while maintaining a slowed progression of disease.

If the researchers are successful, testing NfL levels could help determine if patients can safely remain off treatment because of its ability to predict future relapses.

No FDA approval yet

Although the NfL blood test is not FDA-approved just yet, the agency awarded Breakthrough Device designation to Roche’s Elecsys NfL test for MS in July 2022.

While breakthrough status is promising, it doesn’t guarantee approval. If the NfL test does gain full FDA approval, Roche will already have 75,000 tests available for use around the globe.

Hurdles to the NfL test

Despite the numerous potential benefits the NfL blood test could offer, it also has some clinical limitations.

While NfL is a biomarker of neural damage, it’s not a specific marker of MS. For example, the neural damage it identifies could be associated with other conditions such as stroke, traumatic brain injury, or Alzheimer’s disease.

Researchers also note that other factors such as age, comorbidities, and lesion location could impact the results. In addition, the use of DMTs can skew test results.

Furthermore, NfL levels in those with MS and healthy controls show significant overlap, making it challenging to interpret and use for disease management.

The takeaway

For 13 years, my blood was tested repeatedly for markers of various diseases. But since no blood test capable of aiding in the diagnosis of MS existed, doctors were looking in the wrong areas.

If an NfL blood test had existed when I was searching for a diagnosis, I believe I would have had an answer — and a treatment — much sooner. I’m hopeful that this test, once approved, will prevent future delays in diagnosis for others.

Despite some drawbacks, the NfL blood test holds promise for all of us living with MS. FDA approval of this test will be a day to celebrate. It has the potential to ease diagnosis and make monitoring and treating MS more manageable.