The effect of digital rectal examination on serum levels of prostatic-specific antigen.

Serum prostate-specific antigen (PSA) and acid phosphatase (AP) levels were measured before and after digital rectal examination in 26 patients with varying genitourinary complaints. Prostate examination had no effect on the level of these markers. However, AP levels demonstrated greater within-day, intraindividual variance than PSA levels. Digital rectal examination does not appear to be a source of preanalytical error for serum PSA or AP determinations.