Comparison of two analytical platforms for quantification of neuroglial biomarkers in blood samples: a single...

Advances in ultrasensitive immunoassays have enabled reliable quantification of neuroglial biomarkers in blood, providing valuable insights into neurological disorders. However, cross-platform evaluations are necessary to ensure comparability and standardization. This study aimed to compare the analytical performance of a Single Molecule Array (Simoa) and an ultrasensitive electrochemiluminescence (ECL) assay for quantifying neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) in human serum. Baseline serum samples from 174 participants in the RIFUND trial were analyzed in parallel on both platforms. Concentrations of NfL and GFAP were compared using Spearman correlation, Bland-Altman analyses, reproducibility assessments, dilution linearity, and cross-platform recovery. All samples were quantifiable on both platforms. NfL concentrations correlated strongly between methods (Spearman correlation r = 0.88, p < 0.0001), whereas GFAP correlated moderately (r = 0.77, p < 0.0001). Inter- and intra-assay coefficients of variation were comparable between platforms for both analytes. The relationship between the two assays could be described with the following equations: NfL_ECL = 7.63 × NfL_SIMOA + 1.71 and GFAP_ECL = 0.332 × GFAP_SIMOA + 4.22. Dilution linearity was excellent on both platforms (R² > 0.99), although cross-platform recovery varied systematically across the analytical range. Both Simoa and ECL demonstrated strong analytical performance for neuroglial biomarker quantification in serum. Despite systematic differences in absolute concentrations, relative agreement was high, particularly for NfL. These findings highlight the need for platform harmonization and provide empirically derived conversion factors to support analytical comparability in research and clinical applications.