We developed the first multiplex immunoassay biomarker test for schizophrenia. This test is comprised of 51 immunoassays which allows reproducible identification of schizophrenia patients compared to healthy control subjects with high sensitivity and specificity. Validation of this test consisted of developing a linear support vector machine decision rule and testing the performance using cross-validation. This resulted in readjustment of the panel and algorithm to a smaller set of 40 robust assays, along with a simple procedure for maintenance and recalibration across future measurement changes associated with different reagent lots. The resulting decision rule delivered a sensitive and specific prediction for presence of schizophrenia in subjects compared to matched controls, with a receiver operating characteristic area under the curve of 88%. This multiplexed assay system was launched in 2010 as a CLIA-approved test to aid diagnosis of schizophrenia.