Prostatic Acid Phosphatase (PAP) - Prostatic Acid Phosphatase (PAP) is a component of total acid phosphates and is a major constituent in seminal fluid and is also secreted in the urine. PAP is normally found in serum in very low levels. PAP measurement has found clinical application in the management of prostatic cancer patients. Serum PAP measurements have been useful in monitoring remission or relapse of a prostatic malignancy and in assessing the effectiveness of various treatment regimes.