PROSTATE-SPECIFIC ANTIGEN AS A PREDICTOR OF AN ABNORMAL DIGITAL RECTAL EXAMINATION

Objective To assess the ability of serum prostate specific antigen (PS A) to predict and differentiate patients with normal and abnormal digi tal rectal findings. Subjects and methods A prospective analysis of 13 74 participants in a prostate cancer screening programme was performed . After completion of a questionnaire including age and voiding sympto ms as well as phlebotomy for PSA analysis, digital rectal examination was performed and the findings were categorized with respect to size, consistency, symmetry and nodularity. Results In men less than 50 year s of age the mean serum PSA level failed to discriminate any of the di gital rectal examination categories. In men over 50 there was a statis tically significant difference in mean PSA levels between symmetrical, normal sized prostates and symmetrically enlarged glands as well as b etween symmetrical, normal sized and abnormal prostates (P < 0.05). No statistically significant difference was found in mean serum PSA leve ls between symmetrically enlarged prostate glands and those with palpa ble nodules. PSA levels less than or equal to 2.5 ng/ml (normal range for the Yang polyclonal assay) and < 7.4 ng/ml (corresponding to the n ormal range of < 4.0 ng/ml for the Hybritech monoclonal assay) demonst rated a probability of an abnormal digital rectal examination of 11% a nd 14% respectively. PSA levels > 18.4 ng/ml (corresponding to monoclo nal levels of > 10 ng/ml) had a 67% probability of an abnormal digital rectal examination. However, moderate elevations in PSA could not be used to predict digital examination abnormalities due to the high inci dence of moderate PSA elevations associated with symmetrical enlargeme nt of the prostate. Conclusions Serial annual PSA measurements may pro vide an alternative means of screening men over 50 years of age. Conta mination of results with PSA elevation due to benign prostatic hyperpl asia remains, however, a problem.