Digital rectal examination-associated alterations in serum prostate-specific antigen

The effect of digital rectal examination (DRE) on measurement of serum prostate-specific antigen was investigated during a prostate cancer screening program of 2,736 ambulatory men. Serum samples were collected before and after DRE and values compared using the nonparametric Wilcoxon signed rank test. Small, yet statistically significant, increases were found associated with DRE. The magnitude of these increases, however, was of minor clinical importance. Patients who exhibited the largest increases with initial values greater than the upper limit of normal (4 micrograms/L) were found to have either benign prostatic hyperplasia, prostatitis, or prostatic carcinoma. The benign prostatic hyperplasia patients showed relatively low initial prostate-specific antigen values with similarly small increases related to DRE, whereas the prostatitis and cancer patients exhibited both higher initial prostate-specific antigen values and larger increases associated with DRE. Finally, patients with increases in prostate-specific antigen from less than 4 micrograms/L to greater than or equal to 4 micrograms/L comprised less than 2% of the reference range population, the majority of whom had post-DRE measurements of less than 5 micrograms/L. Thus, DRE does not appear to be a significant factor in falsely elevating prostate-specific antigen levels and should be of limited concern to the clinician obtaining serum samples after DRE.