E.Chassaing, M.Bodnar-Wachtel, T.Schubert, H.Vanderstichele, E.Stoops, and P.Vergnaud
Despite the fact that the core CSF biomarkers (tau, amyloid) reflect on-going pathology in the brains of subjects with Alzheimer’s Disease (AD), new biomarkers are needed to monitor other hallmarks, such as synaptic degeneration. This study documents the analytical performance characteristics of a novel ELISA, targeting P75 truncated Neurogranin, which has been shown to be the most abundant Neurogranin isoform in CSF.
After having performed familiarization runs and adaptation of the test procedures to the needs of a service provider, the assay was challenged internally for its analytical performance characteristics (eg, precision, parallelism, spike-recovery, working range, sample stability) by using commercially available CSF samples (n=32).
The new assay format specifically quantifies Neurogranin truncated at position 75. Full-length Neurogranin is not detected. Neurogranin is quantified in the absence of matrix interference (parallelism 101% ± 8%; dilution range: neat – 1/16). Spike/recovery testing revealed good recovery rates (100% ± 8%). The precision resulted in intra- and inter-assay variability (%CV) below 7% and 13%, respectively. The working range is confirmed between 50 pg/mL (Lower Limit of Quantitation) to 1300 pg/mL (Upper Limit of Quantitation). CSF stability at +4°C is acceptable, but storage at room temperature should not exceed 6 hours; consecutive freezing/thawing of CSF up to 4 cycles did not affect Neurogranin concentrations. The assay format is also applicable to EDTA-plasma samples.
The newly developed Neurogranin TruncP75 colorimetric ELISA assay meets all internal acceptance criteria for clinical trial sample testing and represents an additional tool for patient management.