We randomized the patients’ serum samples across four 96-well plates such that each sample was assayed once. On each plate we included two “Pooled Reference” controls, containing equal volumes of serum from each of the samples. The Proseek® platform also includes three “Interplate controls” for data normalization between plates and three “Negative controls” to establish background levels. One microliter of serum from each of the samples was mixed with the Oncology II reagents following the manufacturer’s protocol, then processed in combination with the Fluidigm® BioMark™ HD high-throughput PCR instrument at the University of Minnesota Genomics Center as previously described (13 (link)). Data generated from the plates were analyzed, including normalization and linearization, per manufacturer protocol. The assay reports relative quantification on a log2 scale, as Normalized Protein eXpression (NPX) values, which are cycle threshold (Ct) values normalized by the subtraction of values for the extension control. All assay characteristics including detection limits and measurements of assay performance and validation are available from the manufacturer’s website (http://www.olink.com/products/).