Comparison of SIMOA and VEUS technologies for serum glial fibrillary acidic protein measurement

Serum glial fibrillary acidic protein (sGFAP) is increasingly studied as a biomarker of astroglial injury, but comparative data between ultra-sensitive analytical platforms are limited. This study evaluated the agreement between the newly developed VEUS technology and the established single-molecule array (SIMOA) method.

A single-centre retrospective analysis was conducted at the Department of Neurology, University Hospital Ostrava. Patients ≥18 years with relapsing-remitting multiple sclerosis, non-inflammatory neurological disorders, or symptomatic controls were included. sGFAP levels were measured using the SIMOA GFAP Advantage PLUS Kit (Quanterix) and the Duplex RUO Kit (GFAP/UCH-L1) (VEUDx, EZDiatech). Method comparison included Spearman correlation, Passing-Bablok regression, and Bland-Altman analysis. Outliers were removed using Tukey's IQR rule.

Fifty-six patients (78.6 % women) were included. SIMOA reported markedly higher sGFAP concentrations (median 110.5 ng/L, IQR 83.2-176) compared with VEUS (median 6.13 ng/L, IQR 3.88-6.87). No significant correlation was observed between platforms (r = 0.02, p = 0.89). Passing-Bablok regression demonstrated a near-zero slope, indicating absent linear association. Bland-Altman analysis showed proportional bias, with VEUS measuring on average 21 % of SIMOA values and increasing divergence at higher concentrations.

These results do not support substituting sGFAP measurements between VEUS and SIMOA assays.