Utility of free prostate specific antigen serum level and its related parameters in the diagnosis of prostate cancer

We evaluated the role of free prostate specific antigen (f-PSA) serum level and its related parameters in detecting prostate cancer. This retrospective study was conducted between January 2006 and March 2008. Trans-rectal ultrasound guided prostate biopsy was performed for 107 patients who had total PSA (t-PSA) level of either > 4 ng / mL with or without palpable nodule or ≤ 4 ng / mL with palpable nodule on digital rectal examination. The performances measurements for f-PSA, percent free PSA (% f-PSA) and free PSA density (f-PSAD) were determined and compared with those for t-PSA and total PSA density (t-PSAD). Descriptive statistics for all variables of interest were calculated, and receiver operating characteristic curves were generated. Nine patients (8.4 %) had normal histology, 69 patients (64.4 %) had benign disease and 29 patients (27.1 %) had prostate cancer. The performance of f-PSA in PCa detection was better than other evaluated parameters. The largest area under the curve for patients in the gray area (t-PSA range 4.1–10 ng / mL) was for f-PSA, with a value of 0.64 and a sensitivity and specificity of 44 % and 87 %, respectively. For % f-PSA, these values were 0.59, 63 % and 62 %, respectively. For patients with a t-PSA level of 10.1–20 ng / mL, they were 0.68, 67 %, and 81 %, respectively, for f-PSA, and 0.64, 67 %, and 76 %, respectively, for %f-PSA. In conclusion, f-PSA serum levels performed better than free to total PSA ratio and t-PSA for prostate cancer screening. It is of clinical value which could affect the biopsy decision avoiding unnecessary interventions.