Vietheer et al measured serum GFAP levels using an immunofluorescence assay and reported that although initially raised serum GFAP concentration does fall after surgery but later in the course of the disease GFAP levels are not predictive of tumor recurrence in patients with GBM.57 To improve diagnostic accuracy, researchers are looking at combined assays of various proteins. Here, GFAP is linked to glioblastoma.