Aims : This study aims to: determine a serum percent free prostate specific antigen (% fPSA) cut-off using the Chiron assay which increases the specificity of PSA testing without detriment to the cancer detection rate. determine the predictive value of % fPSA using the Chiron assay for detecting prostate cancer on repeat prostatic biopsies. Patient and Methods : A retrospective review of transrectal ultrasound (TRUS) and prostatic biopsies performed between August 1997 and October 1998 was carried out. Eighty four consecutive patients with a serum total PSA (tPSA) of 4.1-10.0 ng/ml, a benign feeling prostate gland on digital rectal examination (DRE) and a previous prostatic biopsy negative for prostate cancer were included in the study. Measurements for tPSA and % fPSA were performed with the Chiron ACS tPSA and Chiron ACS 180 fPSA polyclonal antibody immunoassay, respectively. Results : The final cohort consisted of 53 patients, and, 8 of the 53 (15%) patients had prostate cancer diagnosed on repeat prostatic biopsies. The mean % fPSA was significantly lower in patients with cancer (14%) compared to patients without cancer (22%). Using a 20% cut-off for % fPSA, 33% of the negative biopsies could be avoided with a 95% sensitivity for detection of prostate cancer. Conclusion : Percent free PSA is a reliable predictor for detection of prostate cancer on repeat prostatic biopsies. However, individual immunoassays vary in the cut-off of % fPSA needed to provide acceptable sensitivity for prostate cancer detection and need to be clinically validated.
UroOncology
Volume 2, 2002 - Issue 4