A new blood test might help doctors predict whether someone's multiple sclerosis may soon get worse.
The test looks for a substance called neurofilament light chain. It's a nerve protein that can be detected when nerve cells die. People with higher levels of it were more likely to have worsening MS effects within the next year.
"In a disease like MS that is so unpredictable and varies so much from one person to the next, having a noninvasive blood test like this could be very valuable, especially since treatments are most effective in the earliest stages of the disease," lead investigator Ali Manouchehrinia said in a news release from the journal Neurology, where the study was published online May 20.
Manouchehrinia is an assistant professor of clinical neuroscience at the Karolinska Institute in Stockholm, Sweden.
His study of the neurofilament light chain blood test included almost 4,400 people with multiple sclerosis and a control group of more than 1,000 people without it.
In MS, the body's immune system attacks the central nervous system, commonly leading to problems with balance and walking that come and go.
Over five years, volunteers provided blood samples and their health was followed to see whose disability worsened. Researchers also checked for signs of a more serious form of MS called secondary progressive MS, in which disability gets worse little by little and then becomes more constant.
The study controlled the data to account for factors that might lead to worsening disability, such as length of time with MS.
People with MS had far more neurofilament light chain in their blood than did people without the disease, the study found.
And those with high levels of the nerve protein were 40% to 70% more likely to see their disability get worse within the next year compared to those with low levels.
Higher protein levels also translated to a 50% greater chance for a moderate disability that affected everyday life, but not people's ability to walk.
People with higher protein levels were also 50% more likely to develop a disability that impaired walking, but could still walk about one-third of a mile without help or taking a break.
Overall, 16% (525 people) had a moderate level of disability during the five-year study. Nine percent (352 people) developed significant disability.
While the test could predict a much higher risk of disability, it couldn't definitively show whether or not someone would have a disability.
Manouchehrinia said that it's possible that other medical conditions not studied may affect neurofilament light chain levels. More study is needed.
Dr. Asaff Harel, a neurologist at Lenox Hill Hospital in New York City, said the blood test may have a place with current MS monitoring such as MRI and physical exams.
"These results add to the growing body of literature looking at blood neurofilament light chain levels as a tool to predict long-term prognosis in MS," Harel said.
Mark Allegretta, vice president of research for the National Multiple Sclerosis Society, noted that the study was a large one, with more than 1,000 controls.
"This study adds a lot of confidence that neurofilament light chain levels will be useful in MS," he said.
Like Harel, Allegretta also predicted that the blood screening would one day be used in combination with other tests.
"With many of these tools, the information is additive. We're not looking to rely on any single test," he said.
Right now, MRI is used to track the course of the disease. But Allegretta said a blood test has advantages: It's more standardized than an imaging test and could be done more often and for a lower cost.
Allegretta said the test could be useful in clinical studies to see whether someone is responding to a treatment. It is at least a few years away, he added.
Learn more about MS from the National Multiple Sclerosis Society.