These studies evaluated different neurodegenerative disease cohorts, and all showed that the GFAP concentration remains more consistent in serum regardless of FTC stage (up to four) or storage condition, whereas it decreases significantly after only two FTCs in CSF (Abdelhak et al., 2019; Ashton et al., 2021; Simrén et al., 2022; van Lierop et al., 2022; Verberk et al., 2022). Here, GFAP is linked to neurodegenerative disease.