GFAP and primary progressive multiple sclerosis: Only in primary progressive MS (PPMS), serum GFAP correlated strongly with expanded disability status scale (EDSS) (Spearman rho = 0.6, p = 0.002) and with age-related multiple sclerosis severity score (ARMSS) (spearman rho = 0.4, p = 0.04) (Fig. 2).