Prospective evaluation of GFAP point-of-care testing for rapid diagnosis of glioblastoma.

PURPOSE: Glioblastoma is the most common and the most aggressive malignant primary brain tumor. The diagnosis is made by histopathological analysis following stereotactic biopsy or tumor resection. However, rapid diagnostic clarity is often required before histology becomes available. Glial fibrillary acidic protein (GFAP) has been studied as a blood biomarker for glioblastoma using conventional immunoassays. The aim of this study was to test the diagnostic value of a GFAP point-of-care device to differentiate glioblastoma from other brain tumors.

METHODS

Patients admitted to our hospital with a newly diagnosed intracranial lesion suspicious for a brain tumor were enrolled prospectively. Blood samples were collected prior to diagnostic and therapeutic procedures. Plasma GFAP measurements were performed using the TBI plasma test on the i-STAT Alinity® (Abbott) device. The gold standard was the final histopathological diagnosis.

RESULTS

We prospectively enrolled 101 patients (mean age 63 ± 17 years, 44.6% female). GFAP plasma levels were significantly higher in patients with glioblastoma (n = 37; median 610 pg/mL [interquartile range 263.5–1877.5]) compared to other tumors (n = 64; 81.5 pg/mL [40.3–197.3]; p < 0.001). A cut-off point of 191 pg/mL revealed a sensitivity of 84% and a specificity of 75% for diagnosing glioblastoma. A GFAP plasma concentration of > 1000 pg/ml was indicative of glioblastoma with a specificity of 95% and a positive predictive value (PPV) of 82%. Excluding lymphomas further increased the specificity to 96% and PPV to 93%.

CONCLUSION

GFAP measurements using a point-of-care device indicate glioblastoma with high diagnostic accuracy. GFAP testing has the potential to streamline the work-up of brain tumors.