Modern concepts of acid and alkaline phosphatase measurement

Three new assay methods for prostatic acid phosphatase are described relative to results of biochemical methods. Methods for total and isozymes of alkaline phosphatase are also described. Results of a field trial for acid phosphatase tests among multiple institutions in the United States revealed a marked increase in sensitivity for one assay (CIEP) over biochemical methods. which was positive with increasing frequency as the clinical and surgical stage advanced beyond B. Only for stage D did the biochemical method approach the sensitivity of the CIEP assay. The CIEP assay has potential value as a screen for prostate cancer. Another acid phosphatase assay (RIA) proved difficult to perform for many institutions in the field trial. A new solid phase immunofluorescent assay recently introduced may on further testing be more sensitive than the CIEP assay. Total alkaline phosphatase levels studied in patients with advanced disease were markedly elevated in over one-third of the cases. Higher levels were associated with poor survival or response to chemotherapy. Alkaline phosphatase isozyme levels were of added value in locating the site of the increased alkaline phosphatase activity in soft tissue, bone, or liver. Occasionally in the face of a normal total value, increased isozyme activity in one of the aforementioned compartments preceded clinical ability to detect the metastatic foci.