Evaluation of Phi Clinical Performance for the Detection of Prostate Cancer in Routine Clinical Practice

Prostate Health Index (phi) and percent free PSA (%fPSA) are used in patients with a PSA concentration between 4-10 μg/L as an aid to distinguish prostate cancer (PCa) from benign conditions, and to assist in the decision of whether to proceed to biopsy. This study assesses the clinical performance and diagnostic accuracy of phi versus %fPSA in a cohort of Mayo Clinic's patients. Of 4065 phi orders received from May 2017-August 2018, concordance between phi and %fPSA results was evaluated on 2845 results with a total PSA within 4-10 μg/L. Retrospective chart review was performed on 201 Mayo Clinic patients, and %fPSA and phi results were compared with both the decision to biopsy and presence of PCa at biopsy. Receiver operating characteristic (ROC) curve analysis to evaluate the diagnostic accuracy of PSA, %fPSA and phi was performed. In this study 2.5% of the 2845 orders exhibited discordant PCa risk classifications between %fPSA and phi results. In the phi high risk category, 41.7% (versus 26.1% by %fPSA) of patients had biopsy and 100% (versus 66.6% by %fPSA) were positive for PCa. Phi exhibited the highest specificity and ROC area under the curve compared to %fPSA and PSA. phi was a better predictor than %fPSA for finding PCa at biopsy. These findings support continued utilization of phi in the evaluation of patients with a PSA in the 4-10 μg/L range.