Digital Immunoassay Biomarker Detection: the ultra-sensitive Simoa® digital biomarker detection assay from Quanterix is used to quantify the concentration of biomarkers in plasma, serum, and CSF (Quanterix, Billerica, MA). The Simoa platform uses 2.7um antibody labeled beads that bind to individual molecules of analyte and are loaded onto a disc containing 200,000 microwells that each hold only one bead. The immunocomplex “sandwich” is formed with biotinylated detection antibodies that allow for digital and analog detection of analyte at as low as fg/nL concentrations.