Human total tau kit

EDTA plasma samples were collected from the participants, processed and stored at −80°C following standardised procedures. Plasma level concentrations were measured using the Human Total Tau kit (Quanterix, Boston, Massachusetts, USA) with the Simoa HD-1 Analyser (Quanterix, Boston, Massachusetts, USA). Briefly, samples, magnetic beads coated with Tau5 monoclonal capture antibody, and HT7 and BT2 monoclonal biotinylated detector antibodies were combined. Antibody epitopes in the mid-region of tau make the assay sensitive to normal and phosphorylated tau, including most of the known protein isoforms. Thereafter, the capture beads were resuspended with streptavidin-β-galactosidase (SBG) and resorufin β-D-galactopyranoside (RPG) and transferred to the Simoa disk. Each bead fits into a microwell in the disk and if tau has been captured the β-galactosidase hydrolyses the RGP substrate which generates a fluorescent signal whose concentration can be measured against a standard curve derived from known concentrations of recombinant tau. The lower limit of detection for the assay is 0.019 pg/mL and the intra-assay coefficient of variation was 4.7% (all samples were analysed in duplicate on one occasion using one batch of reagents).

Plasma t-tau was measured with the Human Total Tau kit (research use only grade, Quanterix, Lexington, MA) on the Simoa HD-1 analyzer (Quanterix), in accordance with an updated version of the assay described previously that uses a monoclonal capture antibody that reacts with a linear epitope in the midregion of all tau isoforms and a detection antibody that reacts with a linear epitope in the N-terminus of t-tau [28 (link)] [24 (link)]. All samples were analyzed in duplicate on one occasion. (Intra-assay coefficients of variance of the measurements was 5.03%.) All cases and controls were evenly distributed on the examination.