Plasma Aβ Quantification with Simoa

Blood processing for plasma collection was performed within 3 h of blood draw, in the morning under fasting conditions, and stored at −80 °C. Plasma Aβ concentrations were measured employing the Amyblood test on the Simoa platform (HDx instrument, Quanterix) using N-terminal-specific monoclonal antibodies provided by ADx NeuroSciences, as described previously [18 (link),19 (link)]. Briefly, for Aβ1-40, C-terminal-specific ADx103 (2G3, Aβx-40) was used as the capture antibody and N-terminal-specific ADx101 (3D6, Aβ1-x) was used as the detector antibody. For Aβ1-42, C-terminal-specific ADx102 (21F12, x-42) was used as the capture antibody and N-terminal-specific ADx101 was used as the detector antibody. The percent coefficients of variation (CV) of the three quality control samples ranged between 0–4% and 0–19% for Aβ1-40 and Aβ1-42, respectively. The apolipoprotein E (APOE) ε4 genotype status, used as a dichotomous variable (presence/absence), of each study participant was accessed from the DIAN database [20 (link)].