Is prostate-specific antigen the most useful marker for screening in prostate cancer?

Prostate-specific antigen (PSA) and prostatic acid phosphatase (PAP) levels were determined in 241 patients attending the Department of Urology. The population consisted of 140 prostate cancer patients (34 newly diagnosed and 106 under treatment) and 101 patients with benign prostatic hypertrophy (BPH). The diagnostic values of PAP measured by enzymatic assay (EA) and by immunoenzymetric assay (IEMA) appeared to be similar. Elevated PAP (IEMA) levels were found in 10% of the patients with BPH and in 38% of the cancer patients. PSA was measured by immunoradiometric assay (IRMA) and receiver operating characteristic curves were constructed to compare the diagnostic benefits of different cutoff values. PSA (10 micrograms/L) reached a specificity of 88% and a sensitivity of 46%. With a cutoff value of 2.7 micrograms/L, the sensitivity increased to 64%, whereas the specificity fell to 58%. It is concluded that PSA is the most useful marker as a screening test.