Free to total prostate-specific antigen (PSA) ratio improves the discrimination between prostate cancer and benign prostatic hyperplasia (BPH) in the diagnostic gray zone of 1.8 to 10 ng/mL total PSA.

Objectives: Improved discrimination between prostate cancer (PC) and benign prostatic hyperplasia (BPH) is clearly needed. Our aim in this study was to evaluate whether the free to total prostate-specific antigen (PSA) ratio would be useful in the gray zone of 1.8-10 ng/mL total PSA range.

Methods: In a consecutive series of 435 clinic patients referred for prostate evaluation, 308 had a total PSA < 10 ng/mL (92 had PC and 216 BPH). Free and total PSA were measured, and the free to total PSA ratio calculated.

Results: Total PSA values were significantly different between the two groups. For the 200 patients with a total PSA < 6 ng/mL, no significant difference in total PSA values were seen (P = 0.411), whereas free to total PSA ratios remained statistically different (P < 0.001). Receiver operating characteristic (ROC) curve analysis comparing the performances of total PSA over the ratio of free to total PSA showed a clear advantage for the ratio at all sensitivity levels.

Conclusions: These data demonstrate that in a significant number (n = 308) of prostatic patients in the diagnostic gray zone of 1.8-10 ng/mL total PSA, the routine use of free to total PSA might be advantageous in discriminating between cancer and benign hyperplasia. This advantage remained for total PSA < 4 ng/mL. Further study is warranted to confirm these findings in an unselected population.