Rapid recent advancements have led to blood tests (biomarkers) to track multiple sclerosis disease activity. A biomarker is something that can be measured to check normal functioning or the impact of a disease. Blood biomarkers are common in medicine to measure response to therapy such as measuring hemoglobin A1c levels for diabetic control and cholesterol levels for high cholesterol treatment. Injury to nerve cells (neurons) and other cells in the brain and spinal cord can be measured in the blood by checking levels of proteins such as neurofilament light chains (NfL) and glial fibrillary acid protein (GFAP). One panel of these blood markers helps identify people with multiple sclerosis with current active MRI scans. The future of MS biomarkers involves blood tests to diagnose multiple sclerosis, select the best treatment for an individual, and measure treatment response. Barry Singer MD, Director of The MS Center for Innovations in Care, interviews: Tanuja Chitnis MD, Professor of Neurology at Harvard Medical School, is the Director of both MGB Pediatric Multiple Sclerosis Center and Translational Neuroimmunology Research Center at Brigham and Women’s Hospital. She is also Co-Director of the Brigham Multiple Sclerosis Center at Brigham and Women’s Hospital.