[Effects of digital rectal examination on serum prostate specific antigen]

Prostate specific antigen (PSA) level is determined under precise conditions for the detection and follow-up of cancer of the prostate. The question is raised as to whether digital rectal examination has an effect on serum levels and whether an interval of time is required before PSA assay can give reliable results.

A prospective protocol was conducted for 6 months. PSA was assayed in 56 patients hospitalized in an internal medicine ward whose clinical status justified digital rectal examination. Blood samples were taken 2 to 3 hours before the digital rectal examination, performed by the same physician in all cases, then 21 to 22 hours after the examination.

After digital rectal examination, there was a nearly significant increase in PSA level (p = 0.06), an increase which was clinically unimportant (0.25 ng/ml). The levels before and after rectal examination were perfectly correlated and reproducible. These data confirmed those reported in the literature showing marginally significant increases of little or no clinical importance, usually within 2 hours of the examination.

The interval of time between the two assays in our study indicates that in everyday clinical practice, for both inpatients and outpatients, digital rectal examination has no effect on prostate specific antigen and that subsequently there is no need to delay assay.