Serum and bone marrow radioimmunoassay of acid phosphatase in prostatic cancer.

Use of radioimmunoassay (RIA) for determinations of prostatic acid phosphatase has recently received considerable attention because of reported higher sensitivity and specificity than previous enzymatic assays. We have compared the sensitivity and specificity of a commercially available RIA to a highly specific enzymatic assay (thymolphthalein monophosphate) using 37 patients with prostatic cancer and 34 patients with surgically proved benign prostatic hyperplasia. Seventeen of the cancer patients and all 34 of the BPH patients were studied prospectively. We further evaluated specificity by performing the RIA on 25 specimens of bone marrow from patients with nonprostatic disease. Our results indicate the radioimmunoassay is not, at this time, an adequate screening tool, and we question its accuracy in staging patients anymore reliably than by enzymatic assay.