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

## TL;DR

This study evaluates a rapid blood test for glioblastoma using GFAP, showing it can help diagnose the tumor quickly before surgery.

## Contribution

The study introduces a point-of-care GFAP test for rapid glioblastoma diagnosis with high accuracy.

## Key findings

- GFAP plasma levels were significantly higher in glioblastoma patients compared to other brain tumor patients.
- A GFAP cut-off of 191 pg/mL achieved 84% sensitivity and 75% specificity for glioblastoma diagnosis.
- Excluding lymphomas improved the test's specificity to 96% and positive predictive value to 93%.

## Abstract

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.

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.

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%.

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.