NEFL and stroke disorder: However, previous publications have shown that serum NfL tends to increase over the first few days to weeks, in contrast to GFAP, which reaches its peak after approximately 24 h.7,29 Consequently, if it is feasible to assess both biomarkers, an option could be to measure serum GFAP standardized in the acute phase of stroke (such as on day 1 after index stroke) and serum NfL on day 3 respectively 7 after index stroke due to its robustness.