GFAP and astrocytoma (excluding glioblastoma): Nonetheless, regardless of the cause of GFAP protein in serum of glioma patients, that is, damage, specific factors in the biology of the tumor, or the entrance of glioma cells into the circulation, measurements of GFAP levels in serum might be useful in diagnosis of grade IV astrocytoma and prognosis in relation to the progression of the disease.