Immunochemical measurement of serum prostatic acid phosphatase (PAP). Clinical evaluation of radioimmunoassay and counter immunoelectrophoresis.

Two radioimmunoassay procedures (RIA-1 and RIA-2) were evaluated for the quantitation of prostatic acid phosphatase in serum and compared with the enzymatic method and counter immunoelectrophoresis method for their specificity and sensitivity. Sera from 168 patients were analyzed and these included: normals, 27; untreated prostatic cancer patients Stage A, 2; Stage C, 3; Stage D, 17; cancer of prostate treated with different modalities, 42; sarcoma of prostate, 1; prostatitis, 3; nonprostatic carcinoma, 17; and benign prostatic hyperplasia (BPH), 56. RIA-1 procedure appeared more sensitive (82% sensitivity) and specific (94.5% specificity) than the RIA-2 procedure (68% sensitivity and 91.8% specificity), but the differences were not statistically significant. The enzymatic method was found to be least sensitive (63.6% sensitivity) but also the most specific (100% specificity). Only 69 of the specimens were analyzed by counter immunoelectrophoresis, which showed sensitivity of 87% and specificity of 51.4%. False positives were observed more often in patients with nonprostatic cancer and BPH. The variations in diagnostic specificity of immunologic assays suggest the need of characterization of each antibody specificity.