When Martina first noticed her balance getting worse, her doctor found no new inflammation on her brain scan and no relapses to report. Yet something was still quietly advancing. For millions of people with multiple sclerosis, this hidden progression slips past standard tests, even as disability slowly builds over years.
Now, researchers at the University of Basel in Switzerland have found a clue that could change that. A simple blood test measuring a protein called GFAP—short for glial fibrillary acidic protein—may help doctors catch this silent worsening and predict who needs stronger treatment.
GFAP is released by astrocytes, specialized support cells in the brain, when they become activated or injured during progressive disease activity. Unlike another well-known MS marker called NfL, which mainly reflects sudden inflammation and relapses, GFAP appears to capture something different: the slow, creeping damage that happens even when things seem quiet on the surface.
"To treat someone properly, you need to understand what you're treating," said Professor Jens Kuhle from the University of Basel, who led the research. "Our findings suggest progression and inflammation are biologically distinct processes, so they need different markers to track them."
The team analyzed more than 18,000 blood samples from over 2,300 people with MS participating in long-term studies in Switzerland and the United States. In results published in the journal JAMA Neurology, they found that patients with higher GFAP levels were more likely to experience disability worsening over both short and long periods. Even more striking: patients whose GFAP levels dropped after starting MS treatment had a lower risk of future disability progression. Repeated measurements could therefore help doctors monitor whether a therapy is actually working to slow the disease.
"What was particularly noteworthy was that changes in the biomarker during treatment were also associated with patients' later risk of disability progression," said Maximilian Einsiedler, one of the study's first authors. "This suggests that GFAP may capture more than a snapshot—it reflects biological processes that influence the future course of the disease."
The findings strengthen the case for using GFAP in everyday clinical care. Right now, doctors mainly watch for relapses and MRI changes, but GFAP could offer an earlier warning system. If a patient's GFAP levels begin climbing, that might signal the need to adjust therapy before visible symptoms appear.
GFAP still needs further validation before becoming routine. But the research team is optimistic that combining GFAP with the existing NfL test could give doctors a fuller picture of each patient's disease—one marker for inflammation, one for progression. Together, they might help tailor treatment more precisely and speed up the development of new drugs designed specifically for progressive MS.
"This brings us a step closer to clinical implementation," Kuhle said. For patients like Martina, that future may mean fewer surprises and more control over a disease that has spent too long operating in the shadows.