Diagnostic values of digital rectal examination, prostate specific antigen and trans-rectal ultrasound in men with prostatism

Abstract

Objective: To determine the diagnostic values of digital rectal examination (DRE), prostate specific antigen (PSA) and trans-rectal ultrasound (TRUS) individually and in combinations in men aged 50 years and above presenting with prostatism. Design: A prospective, descriptive, cross-sectional, hospital-based study. Setting: The urology ward of Kilimanjaro Christian Medical Centre (KCMC), a 500 bed tertiary hospital in the Kilimanjaro region, Tanzania. Subjects: Ninety four consecutive admissions of men aged 50 years and above admitted with urinary symptoms suggestive of prostatism. Main outcome measures: Primary outcome measures included race and age of patient; Positive predictive values, sensitivities and specificities for DRE, PSA and TRUS individually and in combinations and histology of the prostate specimens submitted after Tru-cut, TURP or open prostatectomy. The secondary outcome measures were mean PSA and PSA density. Results: There was a prostate adenocarcinoma incidence of 25.5%; all found among patients with PSA levels greater than 10ng/ml. The positive predictive value (PPV), sensitivity and specificity of DRE for prostate cancer were 0.67%, 66.7% and 88.6% with an accuracy of 82.8%; while for TRUS, the respective values were 0.58%, 58.3% and 85.7% with an accuracy of 78.7%. PSA alone had a positive predictive value of 0.16. A combination of abnormal DRE and PSA (more than 4.0ng/ml) had a positive predictive value (PPV) of 0.75 while when DRE, TRUS and PSA were all abnormal, the PPV rose to 0.80. Conclusion: A combination of DRE and PSA yields 75% diagnostic sensitivity for prostate cancer and is reliable enough to exempt TRUS where not available since it only adds 5% to this strong diagnostic combination.