Review of Free Prostate-Specific Antigen Assay Utilization at Danbury Hospital

Abstract

Abstract Introduction Measuring the concentration of free fraction of prostate-specific antigen (fPSA) present in serum in addition to the total PSA (tPSA) concentration has been shown to enhance specificity over tPSA alone in evaluating male patients with mild-moderate elevations of tPSA in the diagnostic “gray zone” (4.0-10.0 ng/mL) and negative findings on digital rectal exam. The clinical utility of fPSA has not been demonstrated outside the tPSA gray zone, as the probability of prostate cancer is very low at tPSA <4.0 and very high at tPSA >10.0. However, many clinicians order tPSA and fPSA concurrently without first knowing the results of the tPSA. This study was to review orders for fPSA and provide suggestions for improving utilization. Methods Paired test results for concurrently ordered tPSA and fPSA tests during the time periods of January to February 2018 and January to February 2019 (before and after laboratory information system upgrade) were extracted for quality assurance purposes. No patient identifiers were included. Data were sorted and the percentage of “appropriate” fPSA orders was calculated for each time period. Results The number of concurrent total and fPSA tests ordered was 174 for January-February 2018 and 232 for January-February 2019. The number of tPSA within the 4.0 to 10.0 ng/mL range was 78 for January-February 2018 and 148 for January-February 2019. The percentage of “appropriate” fPSA test orders (tPSA 4.0-10.0 ng/mL) was 44.8% for January-February 2018 and 63.8% for January-February 2019. Conclusion A high percentage of inappropriate fPSA orders was found during both time periods. Inappropriate fPSA testing is not only unnecessary and wasteful but can lead to diagnostic errors. Options for driving improved utilization include automatic canceling of fPSA orders when tPSA is not within the diagnostic gray zone and offering fPSA as a “reflex” test that is performed only when tPSA is within the diagnostic gray zone.