Does rectal examination affect serum acid phosphatase levels?

Formol-stable serum acid phosphatase (SAP) was measured in 200 patients with symptoms of prostatism, before and at varying time intervals after digital rectal examination. In three separate groups of 50 patients SAP levels were measured before and at 5, 15 and 30 min following rectal examination and in a fourth group of 50 patients it was measured before and at 6, 24 and 48 h after examination. No significant change occurred in SAP levels following this examination in any of the groups studied. We conclude that rectal examination does not raise the SAP and that, contrary to popular belief, blood levels recorded at any time within this 48-h period are reliable.