Prostate-specific antigen and the early diagnosis of prostate cancer.

With digital rectal examination (DRE), prostate-specific antigen (PSA) is a major screening tool for prostate cancer. PSA is specific for the prostate, but not for prostate cancer. Multiple factors influence PSA value. Determination of PSA levels is not 100% sensitive for prostate cancer, as PSA levels may be normal despite presence of prostate cancer. The cutoff value for PSA of 4.0 ng/mL gives the highest sensitivity and highest specificity. Several modifications of PSA testing have been developed and may be beneficial for select populations. Uncertainty about the natural progression of prostate cancer and inherent limitations of PSA testing make it unclear whether universal screening is beneficial, and the recommendations of various organizations conflict. Randomized studies are in progress to address the role of PSA testing and of modifications of this test in the early detection of prostate cancer.