Comparative evaluation of various prostate specific antigen ratios for the early detection of prostate cancer

To compare the performance of various ratios using total prostate specific antigen (PSA), complexed PSA (cPSA) and free PSA (fPSA) in the early detection of prostate cancer.

The study included 535 consecutive patients evaluated at a prostate cancer detection clinic between January 1998 and October 1999. Patients had blood samples drawn before transrectal ultrasonography and prostate biopsy to measure PSA, cPSA and fPSA. Receiver operating characteristic (ROC) curves (sensitivity vs 1 - specificity) were used to evaluate the performance of PSA, cPSA, f/tPSA, cPSA/tPSA, fPSA/cPSA, tPSA/prostate volume (PV), fPSA/PV, and cPSA/PV. The areas under the curve (AUC) were calculated for each ratio. The performance of each ratio over all patients or in those with a tPSA of 4-6 or 4-10 ng/mL were evaluated.

Of the 535 patients, 204 (38%) had biopsy-confirmed prostate cancer. The AUC obtained with tPSA alone was 0.64; when measured for all patients the cPSA/PV (0.78), PSA/PV (0.77), f/tPSA (0.76) and fPSA/cPSA (0.75) performed better than tPSA alone. Furthermore, in patients with a tPSA of 4-10 ng/mL, tPSA/PV (0.72), cPSA/PV (0.71), f/tPSA (0.69), fPSA/cPSA (0.69) and cPSA/tPSA (0.62) performed better than tPSA alone (0.52). Finally, in patients with a tPSA of 4-6 ng/mL, PSA/PV and cPSA/PV performed better than the other ratios.

The use of PSA ratios gives a higher sensitivity and specificity for detecting prostate cancer than the use of tPSA alone.