The combination of CSF neurofilament light chain and glial fibrillary acidic protein improves the prediction of long-term confirmed disability worsening in multiple sclerosis

Our objective was to evaluate the individual and combined prognostic attributes of baseline serum and CSF measurements of Neurofilament light chain (sNfL, cNfL) and glial fibrillary acidic protein (sGFAP, cGFAP) on long term clinical outcomes in MS. In this retrospective single center study, patients with serum and CSF stored at first MS presentation and > 15-years of follow-up were analyzed. NfL and GFAP were quantified from cryopreserved samples using a digital immunoassay and analyzed as predictors of confirmed disability worsening (CDW). Sixty patients (70% female) underwent baseline tandem CSF and serum sampling and were followed for a mean of 17.8 years (SD 2.5). 32 developed CDW. By logistic regression, while sNfL cNfL and cGFAP showed prognostic merit (AUC 0.72, 0.70, 0.62 respectively), sGFAP did not (AUC 0.5). The combination of cNfL and cGFAP improved CDW prediction compared to either measure considered in isolation (AUC 0.72). The optimal predictive cut-off for CDW (Youden's index) for cNfL was 596 pg/mL and for cGFAP was 8160 pg/mL. Kaplan-Meier analysis of the cutoff-defined 'high-high' and 'low-low' combined cNfL and cGFAP groupings improved prediction of CDW compared to either marker individually (Hazard ratio 4.5 (95% CI 2.7-18.3), Logrank P < 0.0001). Cox Proportional Hazards regression demonstrated that high baseline cNfL and cGFAP were independently prognostic of subsequent CDW after adjusting for baseline age, sex, EDSS score and subsequent treatment exposure. Each unit increase in Ln(cNfL) and Ln(cGFAP) was respectively associated with an additional hazard of 2.36 (95% CI 1.12-5.52) and 2.26 (95% CI 1.03-5.21). CSF NfL and GFAP are independently prognostic of long-term clinical worsening in MS, and may represent a complementary pairing.