A diagnostic scoring cutoff set at 3 standard deviations above the mean for the normal patient selleck chemicals llc cohort yielded 11% sensitivity for colorectal cancer detection at 100% specificity with these samples. This method of setting cutoffs is commonly used for autoantibody immunoassays (e.g. Liu et al., 2009). Next, to technically validate the VeraCode™ bead assay using the p53 TAA,

we evaluated the data obtained from screening the same patient cohort against beads to which either purified recombinant p53 or cell-free produced p53 was attached (Fig. 2, middle and bottom panels, respectively). The cutoff and scoring were done as with the ELISA. The error bars represent the intra-assay bead-to-bead variance in fluorescence intensity within CDK inhibitor each sample-protein pair (i.e. variance of replicate beads). Results from ELISA were compared to results obtained from VeraCode™ beads. All 5 colorectal cancer samples which scored positive in the ELISA also score positive on both VeraCode™ bead assays (with both recombinant and cell-free p53 protein). In addition, two additional hits in the CRC cohort were detected by the VeraCode™ assay (same two patients detected with both recombinant

and cell-free proteins) but 100% specificity versus the normal patients was maintained. In order to establish intra-assay precision, we performed the multiplex bead assay on triplicate samples of four CRC and four normal patient sera/plasma in a 96-well plate. Two TAAs were used in this multiplexed experiment: The p53 control (discussed earlier) and Cyclin B1 (Koziol et al., 2003, Chen et al., 2007 and Reuschenbach et al., 2009). Each of the three replicate wells of each sample contained approximately 50 beads per TAA. Two previously known p53-positive sera (based on ELISA and VeraCode™ data

in Fig. 2) were chosen for this experiment, whereas their sero-reactivity against CyclinB1 was not known a priori (i.e. positives not necessarily expected based on low diagnostic sensitivity of individual ID-8 TAAs). Results are shown in Supplementary Fig. 2. An average intra-assay CV of 10% across all samples and proteins was achieved (see error bars in Supplementary Fig. 2 for more detail). The diagnostic scoring cutoff for p53 was calculated based on the normal samples as discussed earlier, however, for maximum stringency, the calculations were done before averaging the MFI values of the replicate samples (MFI = Mean Fluorescence Intensity; i.e. mean of all beads within one sample per TAA). With this, the scoring cutoff accounts for variance across the sample replicates. Of note, using this cutoff, previously known p53-positive samples were correctly detected in this VeraCode™ bead experiment, with no false positives (neither in CRC nor normal samples).