Plasma GFAP levels were thus positively correlated with 18F-SMBT-1 uptake in sporadic AD patients compared to control groups [11], but showed no correlation or were even negatively correlated with 11C-DED [5] or GFAP levels in brain tissue [8], suggesting that mechanisms beyond reactive astrocytes or CSF release may contribute to elevated blood GFAP levels [6]. Here, GFAP is linked to Alzheimer disease.