Similar results were obtained with serum samples in which an increase in GFAP levels (detected by sandwich ELISA) was observed in PD patients (n = 23) compared with healthy controls (n = 29) [117] and, again, this increase was more pronounced in PD patients with mild cognitive impairment or dementia than in PD patients with normal cognition [118]. Here, GFAP is linked to Parkinson disease.