Serum prostate-specific antigen: hourly change/24 hours compared with prostatic acid phosphatase.

Simultaneous hourly changes in serum PSA and PAP levels per twenty-four-hour period was studied in 19 urologic patients with no prostatic disease. Serum PSA was determined using Hybritech PSA-R Kits, and PAP was determined using EIA method. PSA and PAP serum levels varied independently from each other. PSA level showed no diurnal variations. The level remained stable with minor variations around a low mean of 0.907 ng/mL, SD 0.09, and CV 9.9% in 16 of 19 (84%) patients, while PAP showed changes consistent with diurnal variations in 5 of those patients. Random variations with no discernible pattern in 7 and remained more or less constant in 4 other patients. Marked random variations in PSA serum level occurred in only 3 patients in the older age group and were accompanied by diurnal variations in PAP level in 2 patients and a constant high level of PAP in 1 patient. The highest PSA level obtained was 6.9 ng/mL which is important when selecting the cut-off level. PSA did not increase appreciably after prostatic massage, and on follow-up PSA returned to premassage level after twenty-four hours (except in 1 patient).