The percentage of free prostatic-specific antigen is also useful in men with normal digital rectal examination and serum prostatic-specific antigen between 10.1 and 20 ng/ml.

Objective: The percentage of free prostatic-specific antigen (PSA) has been introduced as a tool to avoid unnecessary biopsies in men with normal digital rectal examination (DRE) and serum PSA between 4.1 and 10 ng/ml. In this series we also analyze its utility in men with normal DRE and serum PSA between 10.1 and 20 ng/ml.

Materials And Methods: A series of 1149 consecutive men with normal DRE and serum PSA between 4.1 and 20 ng/ml submitted for the first ultrasound guided sextant biopsy is analyzed. In 921 (80.2%) the serum PSA was from 4.1 to 10 ng/ml and in 228 (19.8%) from 10.1 to 20 ng/ml. Total and free serum PSA determinations were done by the inmunoradiometric assays Tandem and Tandem free PSA (Hybritech Inc.).

Results: The overall detection rate of prostate cancer was 27.9%. In the group of men which serum PSA ranged from 4.1 to 10 ng/ml the rate of detection was 25.4% and 37.7% when it was between 10.1 and 20 ng/ml. Using 25% or less of percent free PSA as a criterion for performing prostatic biopsy it would have detected 95.3% and 95.4% of the prostate cancers, respectively. The rate of unnecessary avoided biopsies would be 17.5% when serum PSA ranged from 4.1 to 10 ng/ml and 17.6% between 10.1 and 20 ng/ml.

Conclusions: This prospective study demonstrates that the percentage of free PSA seems to have similar utility when serum PSA levels are between 4.1 and 10 ng/ml and between 10.1 and 20 ng/ml, at the time of the first prostatic biopsy indication.