Additional file 2: Figure S3. of Glutaminyl cyclase activity correlates with levels of Aβ peptides and mediators of angiogenesis in cerebrospinal fluid of Alzheimer’s disease patients

showing method comparison for Aβ determination in CSF of AD patients and SMC: LC-MS (relative quantification) versus MSD Aβ multiplex. Upper panels: scatter plot with Deming regression lines. Lower panels, Bland–Altman plots for Aβ40 assay comparison. For Aβ1-42, only relative quantification was done with LC-MS. LC-MS determinations of Aβ(1–40) and Aβ(1–42) show correlation with both Aβ multiplexes. Coefficients of determination were found to be slightly better with the 6E10 multiplex assays. For the Aβ40 assays, Deming regression lines show slope < 1 and cross the lines of identity in the medium concentration range. Compared with the ELISAs, the LC-MS assay underestimates Aβ40 in the low concentration range and overestimates it at high concentrations. Nevertheless, mean deviation is <5% and there were only 5 out of 60 and 2 out of 60 measurements out of the ±25% range compared with the 4G8 multiplex or 6E10 multiplex, respectively. (TIF 484 kb)