GFAP and astrocytoma (excluding glioblastoma): Eight out of 12 studies report on a significant association of GFAP levels detected in serum (Baumgarten et al., 2018; Gállego Pérez‐Larraya et al., 2014; Ilhan‐Mutlu et al., 2013; Jung et al., 2007; Kiviniemi et al., 2015; Tichy et al., 2016), in microparticles (Sartori et al., 2013), and in mono‐nucleated cells (Muller et al., 2014) isolated from blood of grade IV astrocytoma patients in comparison to lower grade astrocytoma, nonglial tumors, other neurological diseases, and healthy controls.