Efficacy and discriminative ability of prostate-specific antigen as a tumor marker.

A study was performed on 175 men to compare the level of prostate-specific antigen (PSA) in patients with benign prostatic hyperplasia (n = 83) and prostatic carcinoma (n = 92). There was a good correlation between T stage and increasing values of PSA. Using 2.5 ng/ml as the upper normal limit of PSA, the test sensitivity of PSA was 94%, but the specificity only 44%. Receiver-operator characteristic curve (ROC) analysis demonstrates that PSA is superior to prostatic acid phosphatase (PAP); this is particularly true in the higher T stages. Although ROC analysis shows that PSA is more discriminating than PAP, the sensitivity of PSA is dependent upon the choice of an appropriate cut-off point of the test. It was shown that PSA is not sufficient for detecting the presence or absence of prostatic cancer in a general population. However, PSA is the most sensitive marker in the detection of prostatic cancer.