Radioimmunoassay of serum prostatic acid phosphatase after prostatic massage

The effect of prostatic massage on the concentration of prostatic acid phosphatase (PAP) in blood serum as determined by radioimmunoassay (RIA) was compared with that determined by a standard enzymatic assay (EA). Serum was drawn from 24 men before prostatic massage and after—at specified intervals, up to twenty-four hours. Three of these men were young, normal controls; 10 had biopsy-proved prostate cancer (CA); 11 had histologically confirmed benign prostatic hyperplasia (BPH). After prostatic massage, 3 of the 10 CA patients (30%) had elevation of PAP as determined by EA and 4 of the 11 BPH patients (36%) as determined by RIA. None of the controls showed elevated levels of PAP by either assay. In all patients elevated levels of PAP by both assays had returned to normal twenty-four hours after massage. It was concluded that serum for PAP testing by either assay method should be drawn before or twenty-four hours after rectal examination to prevent false positive results and the need for retesting.