Usefulness of free prostatic specific antigen in the detection of prostatecancer

Background: The predictive value of prostate specific antigen for prostate cancer, when levels are between 4 and 10 ng/ml, is low. Within these range of values predictive capacity. Aim: To evaluate the predictive value of the free fraction in subjects with prostate specific antigen values between 4 and 10 ng/ml. Patients and methods: One hundred and forty subjects with pro state specific antigen between 4 and 10 ng/ml were evaluated. All were subj ected to transrectal ultrasound examination with biopsies and the free frac tion of the antigen was measured by enzyme immuno assay. Results: Cancer wa s diagnosed in 36 subjects, all others had a benign prostatic hyperplasia, Mean prostate specific antigen values were 7.4 and 7.1 ng/ml in patients wi th cancer and hyperplasia, respectively. The percentage of free prostatic s pecific antigen was 9.8 and 19.8% in subjects with cancer and hyperplasia r espectively (p<0.001). Using receiver operating characteristic (ROC) curves , a free prostate specific antigen of 13% was the best cutoff value for pre dicting prostate cancer. Conclusions: In subjects with prostate specific va lues between 4 and 10 ng/ml, the measurement of the free fraction of this a ntigen can improve the predictive value of this parameter for the detection of prostate cancer.