Rectal examination and acid phosphatase: evidence for persistence of a myth.

In 1938 Gutman and Gutman' reported raised serum concentrations of acid phosphatase in patients with metastatic carcinoma of the prostate. These serum concentrations were reported also to be raised by prostatic manipulations,2 3 and in particular by rectal examination with or without massage of the prostate.4 6 As a result, medical students have been taught for a long time that blood should not be taken for estimation of enzyme activity for 24 hours after a rectal examination. In the past 10 years, however, there has been a wealth of convincing evidence that rectal examination did not raise the enzyme activity in the absence of carcinoma.2 7 We have recently surveyed hospital doctors' beliefs on this topic and carried out yet another study of the serum enzyme activity before and after rectal examination. Methods The questionnaire asked two questions: is it necessary to delay taking blood for acid phosphatase estimation after rectal examination of the prostate? (Yes, No, Don't know); and if yes, for how long? (up to 1 hour, 1-12 h, 12-24 h, 24-48 h, or up to 1 week). These questions were sent by internal mail to 210 hospital doctors of all grades and specialties at two large district hospitals in the south of England and at a university teaching hospital in the north of England. The replies were anonymous, a code having been included that identified only the hospital grading and whether the responder was "medical" or "surgical." Thirty-six patients with no known prostatic disease admitted to a general surgical ward gave informed consent to be included in the study. Seven-10 ml of blood was drawn from a suitable arm vein five minutes before a routine digital rectal examination during which the prostate was carefully palpated but not massaged. The examination, which was made as uniform as possible, lasted about 30 seconds. Blood samples were drawn at 5 minutes, 1 hour, and 24 hours after the rectal examination. The blood was transferred to a plain universal container.12 The serum was separated immediately and stored at-20°C. The assays were performed within one week and all the four specimens from each patient were analysed in the same batch. Total (TAP) and tartrate-inhibited (=prostatic fraction, PF) acid phosphatase activity was determined by the method of Richterich et al,13 using p-nitrophenylphosphate as substrate (Roche, Diagnostica). The method depends on the hydrolysis ofp-nitrophenylphosphate to phosphoric acid and p-nitrophenol, the latter being measured photometrically …