The role of prostate-specific antigen as part of the diagnostic triad and as a guide when to perform a biopsy.

The authors reviewed the results and relationship of prebiopsy prostate-specific antigen (PSA) assay, digital rectal examination (DRE), and transrectal ultrasound (TRUS) in 124 consecutive patients who underwent a prostate biopsy because of abnormal results of either DRE or TRUS. Results of the three tests (PSA, DRE, and TRUS) showed abnormalities in 54%, 75%, and 84.6% of patients, respectively; biopsy results were positive for cancer in 45.2%. Cancer detection rate increased as the PSA value increased from less than or equal to 4 ng/ml (17.5%) to more than 4 ng/ml (68.7%) to more than 20 ng/ml (83.3%), and as the number of positive tests increased (6.9% for one, 32.7% for two, and 82.6% for three). The PSA assay was the most important parameter of the diagnostic triad. These results suggested that regardless of DRE and TRUS findings, PSA less than or equal to 4 ng/ml confers a low prostate cancer risk, PSA more than 4 ng/ml but less than or equal to 10 ng/ml confers an intermediate prostate cancer risk, and PSA more than 10 ng/ml confers a high prostate cancer risk. Regardless of other findings, all patients with a PSA value more than 10 ng/ml require biopsy because of the high likelihood of cancer. All patients with abnormal DRE or TRUS results still require biopsy despite a low index of suspicion of prostate cancer when the PSA value is less than or equal to 4 ng/ml.