9 Development of a Rapid Lateral Flow Assay for Early Identification of Glioblastoma and Brain Metastases Using a Circulating Serum Biomarker

Abstract Introduction Rapid diagnostic tools could improve the early detection of glioblastoma (GBM) and brain metastases (BM). Lateral flow assays (LFAs) offer a simple, point-of-care testing platform. Glial fibrillary acidic protein (GFAP) has previously been reported as a circulating marker associated with blood–brain barrier disruption in brain tumours. This study aimed to develop and evaluate an LFA capable of detecting GFAP in the serum of patients with GBM and BM. Methods Detection antibodies were conjugated to universal gold nanoparticles to generate a sandwich-format GFAP LFA test strip. The assay was evaluated using serum samples from patients with GBM (n = 20), BM (n = 12), and non-tumour controls (n = 30). Test line signal intensity was quantified using Fiji/ImageJ software. Serum GFAP concentrations were also measured using Single Molecule Array (SIMOA®) technology as a reference method. Results Positive LFA test bands were observed in 95% of GBM samples (19/20), 83% of BM samples (10/12), and 30% of control samples (10/30). Mean test band intensities were 11,408 arbitrary units (a.u.) for GBM, 11,206 a.u. for BM, and 14,072 a.u. for controls, indicating an approximate false-positive rate of 30%. SIMOA® analysis detected GFAP in all samples across all groups, with mean serum concentrations of 2,533 pg/mL in GBM, 644 pg/mL in BM, and 45 pg/mL in controls. Conclusion This study demonstrates the successful development of a highly sensitive GFAP lateral flow assay for detecting blood–brain barrier disruption in GBM and BM. While the assay shows strong sensitivity, a false-positive rate remains and will be addressed through further optimisation in future work.