Comparison of total, complexed and free prostate-specific antigens and their ratios in the detection of prostate cancer in a non-screened population

Background The role of prostate-specific antigen (PSA) isoforms in the detection of prostate cancer in a non-screened population in the UK remains to be determined. Methods Consecutive patients undergoing diagnostic transrectal ultrasound-guided biopsy of the prostate were studied. Prior to biopsy, a blood sample was obtained and total, complexed and free PSA concentrations measured. Results Of the 171 patients included in the study, 103 were found to have prostate cancer. There were significant differences in total and complexed PSA concentrations and in the ratio of free-to-total PSA (all P < 0.001) between patients with prostate cancer and those with benign disease. Receiver operating characteristics (ROC) curve analysis showed that the corresponding areas under the curves were similar. Restricting the analysis to the 77 patients who had total PSA concentrations between 2 and 10 mug/L, ROC curve analysis showed that total and complexed PSA concentrations failed to discriminate between benign and malignant disease. In contrast, the areas under the ROC curve were greater for the free-to-total ratio (P = 0.033). Conclusion These results show that in patients with total PSA concentrations between 2 and 10 mug/L, the free-to-total PSA ratio was superior to total PSA concentration in discriminating between patients with benign and malignant disease.