A Solid Phase Radioimmunoassay for Prostatic Acid Phosphatase

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Abstract
The sensitivity of a recently developed solid phase radioimmunoassay for human prostatic acid phosphatase was compared to that of an enzymatic method using p-nitrophenylphosphate as substrate. In 109 histologically verified untreated state I-IV prostatic cancers and 200 men without such cancer the solid phase radioimmunoassay method demonstrated substantially greater sensitivity and specificity than the enzymatic technique. In the 109 prostatic malignancies the immunochemical method correctly classified 80 (70%) vs. 34 (31%) for the p-nitrophenylphosphate enzymatic technique (P < 10-6). In 44 stage I and II cancers confined to the prostate the radioimmunoassay was abnormally elevated in 19 (43%) with only 4 (9.1%) enzymatic elevations (P < 10-3). In 65 stage III and IV extraprostatic cancers correct classifications were noted in 61 (94%) of the radioimmunoassays and 30 (46%) enzymatic tests (P < 10-6). The radioimmunassay in 200 male controls yielded 11 (5.6%) and the p-nitrophenylphosphate enzymatic test yielded 7 (3.5%) falsely positive results. In 90 nonprostatic human cancer sera 85 (94.5%) were correctly classified as negative by the radioimmunoassay for prostatic acid phosphatase vs. 66 (73%) as negative by the enzymatic method. These data are discussed in terms of the merits of a radioimmunochemical approach for the measurement of human serum prostatic acid phosphatase.