Value of free-to-total prostate-specific antigen ratio for detection and staging of prostate cancer

Background. We aimed to evaluate the clinical usefulness of measurement of the free-to-total (F/T) ratio of prostate-specific antigen (PSA) for the differentiation of prostate cancer from benign prostate hyperplasia (BPH) and for the staging of prostate cancer. Values for PSA density (PSAD) and PSAD adjusted to the transition zone volume (PSADT) were also evaluated in patients with mildly elevated PSA levels (4.1-10 ng/ml). Methods. Total and free PSA and the F/T ratio were determined in 80 men with prostate cancer and 48 men BPH before treatment. PSA levels were measured with a chemiluminescent enzyme immunoassay. Results. Patients with prostate cancer had a significantly lower F/T ratio than those with BPH. A cut-off value of 14% for the F/T ratio provided a positive predictive value of 81.6% and a negative predictive value of 65.4%. The F/T ratio did not differ between patients with clinically localized and metastatic prostate cancer. In patients with a PSA value of 4.1-10ng/ml, a cut-off value of 14% for the F/T ratio provided a sensitivity of 66.7% and a specificity of 76.2%. Sixty percent of the missed cancer in patients with an F/T value of 14% or more could be rescued using the PSAD value. Conclusion. Measurement of the F/T PSA ratio has good sensitivity and specificity in distinguishing prostate cancer from BPH, especially in patients with a PSA level of 4.1-10ng/ml. However, compared with serum PSA level, the F/T PSA ratio is not valuable for the clinical staging of prostate cancer.