Dichotomous Estimation of Prostate Volume: A Diagnostic Study of the Accuracy of the Digital Rectal Examination

PURPOSE: To assess the diagnostic reliability of a dichotomous digital rectal examination (DRE) tool in assessing prostate volume (PV) compared to gold-standard transrectal ultrasound (TRUS) volume measurement. MATERIALS AND METHODS: Male patients presenting to a single tertiary referral centre urology practice requiring TRUS were prospectively recruited between January 2010 and August 2011. Size was estimated by DRE immediately prior to TRUS measurement. DRE measurements were classed into four groups: <30 mL , 30 to 49 mL, 50 to 99 mL and >100 mL. The primary outcomes were sensitivity, specificity, and the positive and negative likelihood ratios for a 30 mL cut-off. RESULTS: Three hundred and three patients were recruited to the study. The median age of the study group was 64.9 years. On TRUS analysis, 244 patients had a PV larger than 30 mL and 139 of them, larger than 50 mL. The median PV was 47 mL with a median International Prostate Symptom Score of 10 and prostatic specific antigen (PSA) of 5.7. When analysed for the ability to identify a gland larger than 30 mL, DRE had a high sensitivity and low negative likelihood ratio. The median PSA level (ng/L) for prostates measured by DRE with a 30 mL cut-off was significantly different with higher median PSA values for volumes larger than 30 mL. CONCLUSIONS: DRE is a reliable tool for dichotomous assessment of prostatic volumes above 30 mL and 50 mL. These results illustrate the value of re-examining the role of categorical DRE estimations in benign prostatic hyperplasia patients.