A comparative study on the diagnostic value of prostatic acid phosphatase (PAP) and prostatic specific antigen (PSA) in patients with carcinoma of the prostate gland

Serum prostatic-specific antigen (PSA) and prostatic acid phosphatase (PAP) were determined simultaneously in 241 patients presented to the Urology Department. The patients consisted of 140 prostatic carcinoma patients (34 newly diagnosed and 106 previously treated) and 101 patients with benign prostatic hypertrophy (BPH). Prostatic acid phosphatase was measured by two different methods, an enzymatic method (PAP-EA, Boehringer) with tartrate inhibition and an immunoenzymetric assay (PAP-IEMA, Hybritech). The concentration of prostatic specific antigen in serum was measured using a recently introduced immunoradiometric assay (PSA-IRMA, Hybritech). Receiver operating characteristic curves were constructed to compare the diagnostic value of the different tests at different cutoff values. The diagnostic efficiencies of the PAP-EA and the PAP-IEMA appeared to be similar. A better diagnostic efficiency for PSA compared to PAP was found independent of the cutoff value. The upper-normal limit of 2.7 micrograms/l for PSA, as suggested by the manufacturer and mentioned in the literature introduces too many false-positive results. We therefore selected 10 micrograms/l as the upper-normal limit for PSA (sensitivity 57%, specificity 88%). Combined sensitivity found for PAP + PSA was 37% with a specificity of 97%. A literature survey is included to allow better comparison with data published elsewhere.