Comparison of Two Platforms for the Measurement of Fg/ml Concentrations of Protein Biomarkers Using Single Molecule Arrays and Digital ELISA: the Benchtop Reader Quanterix SR-X™, and the Fully Automated Analyzer HD-1™

Digital ELISA (Enzyme Linked Immunosorbent Assay) based on single molecule arrays (Simoa) has improved sensitivity of traditional ELISA from picomolar (10−12M) to femtomolar (10−15M), increasing the quality and quantity of biomarkers that can be measured for health and disease. Digital ELISA counts signal generated from single immunocomplexes formed on superparamagnetic beads confined in arrays of femtoliter-sized wells in which fluorescent molecules are highly concentrated. Quanterix has developed digital ELISA assays in a fully-automated instrument (Simoa HD-1 Analyzer), ideal for use in pharmaceutical companies, drug discovery, clinical research and other areas necessitating full automation and high throughput. Recent advancements in the Simoa technology and workflow have been integrated into the new SR-X benchtop reader, with a smaller footprint and more flexible workflow. Operators prepare assays in microtiter plates at the bench in a semi-automated format similar to traditional ELISA, with the notable exception that plates are preserved by drying after assay completion, and can be read immediately or the next day. We present results comparing performance of the following Simoa assays on SR-X to HD-1: PSA; HIV p24; Tau; Neurofilament-light; PD-L1; TNFa; IL-10; IL-17A; IL-6 and a neurology multiplex panel consisting of NF-L, tau, GFAP and UCH-L1. Measured sample levels correlated with R2 values from 0.96 to 1.00, with average LOD and LLOQ within 1.4 and 1.5 fold of HD-1, respectively. Inter-assay precision ranged from 4.0 to 11.2% CV across assays. Operators tested full-plates from start to finish within 1 – 2 hours (1/2 hour hands on time) and a read time of 2 hours (5 minutes hands on time).