Bdnf discovery kit

Plasma samples were thawed at room temperature and centrifuged at 10,000 x g for 5min prior to assay. Plasma Aβ40, Aβ42, BDNF, GFAP, pTau-181, and NfL concentrations were measured with Simoa (Single Molecule Array) assay kits on an HD-X analyzer (Quanterix, Billerica, MA USA). BDNF (BDNF Discovery Kit, # 102039), pTau-181 (pTau-181 Advantage V2.1 Kit, #104111), and Aβ40, Aβ42, NfL, GFAP (Neurology 4-Plex E Advantage Kit, #103670) kits were assayed according to manufacturer protocol (Quanterix, Billerica, MA USA). All samples were run in duplicate and each assay performed in the same batch. Assays were performed by the same technician blinded to the participant’s state and clinical data. Data were exported from the instrument for biomarker analysis. Subjects were not informed of their biomarker results due to their experimental nature, and this was pre-specified in the consent.

BDNF measurements in serum samples were performed using the BDNF Discovery Kit single-molecule array assay (Simoa^®) from Quanterix (Cat no. 102039). Calibrators, participant samples, and two quality control samples per plate were measured in duplicate using a 2-step assay on a Simoa SR-X platform (Quanterix) according to manufactures protocols. Serum samples were diluted 1/1,000. The intra-assay concentration coefficient of variation was calculated for the duplicates of each participant sample and if they were more than 20% the sample was remeasured as per De Wolf et al. (2020 (link)). The intra-assay coefficient of variation for included sample measures was 7.2%. The median values for bi-participant replicates were then calculated and if the absolute difference between a replicate and the median value exceeded 10% of the median, the replicate was treated as an outlier and deleted from the statistical analysis. The mean of each biomarker concentration was then calculated for each participant sample.