NEFL and Alzheimer disease: Previous research also suggests that GFAP may be a sensitive marker for astrogliosis related to amyloidosis in Alzheimer’s disease35 but less useful in non-Alzheimer’s disease pathologies, including PSP.22 This, paired with the lack of statistically significant associations between PSPRS scores and survival, suggests that clinical trials using NfL as an outcome of interest may achieve meaningful interpretation of the results with smaller sample sizes, at least at a group level.