5053 Background: We describe the clinical performance of a novel protein structural assay for prostate cancer (CaP) diagnosis. The assay uses Solvent Interaction Analysis (SIA) to accurately detect changes in PSA isoform composition that differentiate benign and malignant disease, independent of total serum PSA (tPSA). Methods: From January 2007 to September 2008, men already undergoing biopsy for accepted clinical criteria at 3 sites [University Hospitals Case Medical Center (Cleveland); Cleveland Clinic (Cleveland); and Veterans Administration Hospital (Boston)] were enrolled in an IRB approved study. Prior to standard transrectal ultrasound (TRUS) guided biopsy, patients received a digital rectal examination with systematic prostate massage followed by collection of voided urine for use in PSA/SIA. The assay determined the relative distribution of the entire heterogeneous PSA isoform population between two coexisting aqueous phases for diagnostic purposes. Results: 222 men were enrolled in the trial. Biopsy results were classified as case (malignant, n = 100) or control (benign, n = 122). Receiver operating characteristic performance results demonstrated AUC of = 0.88 for PSA/SIA and 0.58 for tPSA. At a cut-off value of the composite structural index K = 1.73, PSA/SIA displayed sensitivity = 100%, specificity = 80%, PPV = 83%, and NPV = 100%. For the same patients at tPSA cut-off level of 4 ng/ml, the sensitivity = 82%, specificity = 27%, PPV = 54%, and NPV = 87%. Conclusions: PSA/SIA uniquely exploits the inherent structural heterogeneity in PSA resulting in superior diagnostic performance over conventional biopsy selection criteria. We hypothesize that the high specificity of PSA/SIA is actually underestimated by standard prostate biopsy sampling error. Future trials will assess the utility of the assay in the surveillance of CaP patients after definitive local therapy and other applications in the diagnosis and management of CaP. [Table: see text]
Prostate-specific Antigen/Solvent Interaction Analysis: A Preliminary Evaluation of a New Assay Concept for Detecting Prostate Cancer Using Urinary Samples
