Serum-to-Urinary Prostate Specific Antigen Ratio: Its Impact in Distinguishing Prostate Cancer When Serum Prostate Specific Antigen Level is 4 to 10 ng./ml.

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Abstract
Benign prostatic hyperplasia (BPH) was shown to be associated with high concentrations of urinary prostate specific antigen (PSA). We investigated the serum-to-urinary PSA ratio in patients undergoing prostate biopsy to assess its efficacy in enhancing serum PSA specificity in the detection of prostate carcinoma. From November 1995 through January 1996 consecutive patients undergoing prostate biopsy were prospectively included in the study. Serum and urine PSA levels were measured at our laboratory with the Tandem-R assay. Samples were drawn 24 hours before prostate biopsy and at a distance from prostatic manipulation or ejaculation. We studied 73 patients with BPH and 57 with prostate cancer. Differences between BPH and prostate cancer were statistically significant considering serum PSA or serum-to-urinary PSA ratios. In the 50 patients with a serum PSA of 4.0 to 10.0 ng./ml. (35 with BPH and 15 with prostate cancer) the differences between prostate cancer and BPH were still significant only when considering serum-to-urinary PSA ratio. Receiver operating characteristic curves showed that serum-to-urinary PSA ratio was a better predictor of prostate cancer than serum PSA. Our results suggest that the serum-to-urinary PSA ratio may be useful in distinguishing BPH from prostate cancer, particularly in the diagnostic gray zone of serum PSA between 4.0 and 10.0 ng./ml.