Prospective Evaluation of Prostate Specific Antigen and Prostate Specific Antigen Density in the Detection of Carcinoma of the Prostate: Ethnic Variations

Abstract

We evaluated prospectively the ethnic variations in prostate specific antigen (PSA) and prostate specific antigen density in the detection of carcinoma of the prostate. A total of 297 consecutive patients with an elevated serum PSA and/or abnormal digital rectal examination underwent transrectal ultrasound with lesion directed and systematic biopsy (6 if the prostatic volume was 50 cc or less and 12 if it was greater than 50 cc). Receiver operating characteristic curves, predictive values and likelihood ratios were calculated for PSA and PSA density for white and black patients. Ethnic analysis was performed for the entire group, patients with a normal digital rectal examination, and those with a normal digital rectal examination and PSA of 4 to 10 ng./ml. Of the 297 patients 131 (44%) had cancer, including 48 of 97 black (50%) and 83 of 200 white (42%) patients. Median PSA, PSA density and prostate size did not differ between the positive or negative biopsy groups, or between the ethnic groups in any of the analyses. If all digital rectal examinations were considered PSA density was superior to PSA by receiver operating characteristic analysis for cancer detection in both ethnic groups when all values or PSA of 4 to 10 ng./ml. were considered. However, the significance was lost if only patients with a normal digital rectal examination were considered. In general, predictive values were greater in black patients. Likelihood ratios for a negative test result in black patients demonstrated significant changes in the post-test probability if a PSA density cutoff of 0.1 was used to determine the need for biopsy. Many unnecessary biopsies could be avoided and few cancers would be missed. A PSA density cutoff of 0.1 may be warranted in determining the need for prostate biopsy in black men with a normal digital rectal examination.