Investigation of glial fibrillary acidic protein (GFAP) in body fluids as a potential biomarker for glioma: a systematic review and meta-analysis

Introduction Liquid biopsies are promising diagnostic tools for glioma. In this quantitative systematic review, we investigate whether the detection of intermediate filaments (IF) in body fluids can be used as a tool for glioma diagnosis and prognosis. Materials and methods We included all studies in which IF-levels were determined in patients with glioma and healthy controls. Of the 28 identified eligible studies, 12 focussed on levels of GFAP in serum (sGFAP) and were included for metadata analysis. Results In all studies combined, 62.7% of all grade-IV patients had detectable levels of sGFAP compared to 12.7% of healthy controls. sGFAP did not surpass the limit of detection in lower-grade patients or healthy controls, but sGFAP was significantly elevated in grade-IV glioma (0.12 ng/mL (0.06 - 0.18), P < 0.001) and showed an average median difference of 0.15 ng/mL (0.04 - 0.25, P < 0.01) compared to healthy controls. sGFAP levels were linked to tumour volume, but not to patient outcome. Conclusion The presence of sGFAP is indicative of grade-IV glioma, but additional studies are necessary to fully determine the usefulness of GFAP in body fluids as a tool for grade-IV glioma diagnosis and follow-up.