Figure 1A compares serum NfL concentration among the three groups of subjects, and Figure 1B compares serum GFAP concentration among the three groups of subjects. Serum NfL levels in both MCI and AD groups were higher than those in HC group, and the difference was statistically significant (p < 0.05), but there was no difference between the MCI and AD groups (p > 0.05). Serum GFAP levels in the MCI and AD groups were significantly different from those in the HC group, and GFAP could distinguish between MCI and AD (p < 0.01). Here, NEFL is linked to Alzheimer disease.