Clinical utility of serum prostatic acid phosphatase measurements for detection (screening), diagnosis, and therapeutic monitoring of prostatic carcinoma; assessment of monoclonal and polyclonal enzymes and radioimmunoassays.

Serum prostatic acid phosphatase (PAP), measured by three different technics, was used to screen 560 men over 50 years of age for prostatic cancer. All three PAP procedures failed to detect the one subject found to have prostatic cancer on physical examination and confirmed by biopsy, and all assays had a significant number of "falsely" elevated PAP levels. Four PAP assays were assessed in 80 men undergoing prostatic biopsy/removal in whom histologic examination of prostatic tissue was made. Clinical sensitivity and specificity for detecting those patients with and without prostatic cancer ranged from 20-57% and 54-95%, respectively, with the monoclonal enzyme immunoassay being the most sensitive but the least specific, and the traditional enzyme assay being the most specific but insensitive. In men with diagnosed prostatic cancer undergoing radiation or chemotherapy, the assays were useful in distinguishing between those with active and inactive disease. The authors conclude that serum PAP assays, irrespective of the type of procedure used, has no place in screening for prostatic cancer, a minimal role in establishing a definitive diagnosis, but a useful role in monitoring therapy.