Glial fibrillary acidic protein: a potential biomarker for progression in multiple sclerosis

The major intermediate cytoskeletal protein of astrocytes, glial fibrillary acidic protein (GFAP), and that of axons, neurofilament light protein (NFL), may both be released into the cerebrospinal fluid (CSF) during pathological processes in the central nervous system (CNS). We investigated GFAP and NFL levels in CSF as possible biomarkers for progression in multiple sclerosis (MS). Patients with relapsing-remitting MS (RRMS, n = 15) or secondary progressive MS (SPMS, n = 10) and healthy control subjects (n = 28) were examined twice with an interval of 8-10 years apart. Neurological deficits were scored with the Expanded Disability Status Scale (EDSS). GFAP and NFL levels were determined in CSF by enzyme-linked immunosorbent assay (ELISA). GFAP levels and NFL levels correlated with age (r and r (s) = 0.50, p = 0.006). Adjusting for age, MS patients had increased GFAP levels compared with controls (p = 0.03) and GFAP levels correlated with neurological disability (EDSS, r = 0.51, p < 0.05) and disease progression [Multiple Sclerosis Severity Score (MSSS), r = 0.47, p < 0.05]. The mean annual increase of GFAP was 6.5 ng/L for controls, 8.1 ng/L for RRMS patients, and 18.9 ng/L for SPMS patients. GFAP level at the first examination had predictive value for neurological disability 8-10 years later (EDSS, r = 0.45, p < 0.05) but not for EDSS increase between the examinations. NFL levels were not significantly increased in MS patients compared with controls and had no relationship to disability or progression and no prognostic value for disability development. GFAP, a marker for astrogliosis, is a potential biomarker for MS progression and may have a role in clinical trials for assessing the impact of therapies on MS progression.