Simoa nf light advantage

Simoa™ NF-light^® Advantage (Quanterix, Billerica, MA, USA) kits were used according to the manufacturer’s instructions. Samples pre-treated with GuHCl were processed as for the NT1- and FL-tau assay except NfL diluent was used. The LLoQ in the presence of 0.25 M GuHCl was 1.39–1.56 pg/mL. The repeatability of the NfL assay for two internal control samples was determined as 4.0% and 3.3%.

The Simoa® Aβ42 Advantage (Quanterix, Billerica, MA, USA) and Simoa™ NF-light® Advantage (Quanterix, Billerica, MA, USA) kits were used according to the manufacturer’s instructions. Reagents from a single lot were used for analysis of all specimens from either the PRECISION study cohort or the Down syndrome study cohort. To determine the optimal dilution factor, plasma samples from 73 healthy donors were diluted 1:4 and 1:8 and analyzed for Aβ1-42 and NfL, and the highest dilution factor that allowed reliable quantification of samples was used. Thereafter, specimens were diluted 1:8 for Aβ42 and 1:4 for NfL. As with specimens for the NT1 assay, plasma was centrifuged at 14,000×g for 4 min; the upper 90% transferred to a new Eppendorf protein lobind tube and diluted with sample diluent provided in the kits. LLoQs for the Aβ1-42 and NfL assays were calculated as described for the NT1 assay and were 0.41 pg/mL and 0.47 pg/mL, respectively. The average %CV for all samples measured in the study was 5.5% for the Aβ1-42 and 7.5% for the NfL assay.

EDTA plasma samples were collected, aliquoted, and stored at −80 °C according to standard procedures [33 (link)]. The pl-NfL, pl-tau, and pl-GFAP were measured with the SiMOA NF-light advantage, SiMOA Human t-tau, and SiMOA GFAP Discovery Kits (i.e., the same used for CSF GFAP quantification) on the SiMOA SR-X platform (Quanterix). The mean intra-assay and inter-assay CVs were 4% and 12% for pl-NfL, 5% and 10% for pl-tau, and 5% and 11% for pl-GFAP.