Dose–response and technical specificity for candidate biomarkers. Technical specificity is assessed by comparing standard curves prepared from a serial dilution of antigen mixes with (specific) or without (unspecific) the specific antigen present. These different solution mixes are PBS + 0.1% BSA ± antigen (Additional file 1: Table S4). The x-axis shows the antigen concentrations in the different mixes. The y-axis shows Cp-values, which were normalized to the internal control GFP by subtracting each biomarker value from the GFP-value for this sample. As indicated, each assay was tested by three different specific antigen mixes and a single unspecific antigen mix, which indicate the background of the assay.