Nomogram for predicting the probability of the positive outcome of prostate biopsies among Ghanaian men

Abstract

Introduction and objectives: Several existing models have been developed to predict positive prostate biopsy among men undergoing evaluation for prostate cancer (PCa). However, most of these models have come from industrialized countries. We therefore, developed a prostate disease nomogram model to provide a basis for predicting a prostate biopsy outcome by correlating clinical indicators and diagnostic parameters among Ghanaian men. Subjects and methods: The study was a hospital-based cross-sectional prospective one which was undertaken at the Department of Surgery (Urology Unit) Komfo Anokye Teaching Hospital (KATH) from December, 2014 to March, 2016. In all a total of 241 patients suspected of having a prostate disorder due based on an abnormal digital rectal examination (DRE) findings and, or elevated prostate specific antigen (PSA) level underwent Trans-Rectal Ultrasonography (TRUS) guided biopsy of the prostate. Stepwise logistic regression was used to determine the independent predictors of a positive initial biopsy. Age, prostate-specific antigen (PSA), digital rectal examination (DRE) status, prostate specific antigen density (PSAD), history of alcohol consumption and history of smoking findings were included in the analysis. Two nomogram models were developed that were based on these independent predictors to estimate the probability of a positive initial prostate biopsy. Receiver-operating characteristic curves (ROC) were used to assess the accuracy of using the nomograms and PSA and PSAD levels for predicting positive a prostate biopsy outcome. Results: Prostate cancer was diagnosed in 63 out of 241 patients (26.1%). Benign prostatic hyperplasia was diagnosed in 172 (71.4%) of patients and the remaining 6 patients (2.48%) had chronic inflammation. Significantly elevated levels of PSA and PSAD were observed among patients with PCa compared to patients without PCa (p < 0.05). Furthermore, it was observed that age, DRE, PSA, PSAD, history of smoking, and history of alcohol consumption were significantly independent predictors (p < 0.05) of prostate cancer. The area under the receiver operating characteristic curve (AUC) of nomogram I and II were 87.3 and 84.8 respectively which were greater than that of total PSA (AUC = 75.8) and PSAD (AUC = 77.8) alone for predicting a positive initial prostate biopsy Conclusion: We conclude that, nomograms offer a better and accurate assessment for predicting a positive outcome of prostate biopsies than the use of traditional tools of PSA, DRE and PSAD alone. Keywords: Nomogram, Prostate biopsy, Prostate specific antigen (PSA), Prostate specific antigen density (PSAD)