肛診，經直腸前列腺超音波及前列腺特殊抗原目前已廣泛地被應用於前列腺癌的診斷。在本研究中我們欲比較其中之差別並定出臨床診斷前列腺癌實際應用流程。在本研究中共有接受前列腺切片的病患353位列入分析。而診斷流程是以切片結果的陽性預測值來決定。當三種診斷工具中的二種是正常時，診斷出前列腺癌的機會相當小。反之，如其中二種為異常時，則癌症的可能性很高。肛診及前列腺特殊抗原是結合兩種診斷工具中最好的一種組合。系統性切片比單獨針對異常部位切片可造成幾乎兩倍的陽性率。如肛診及前列腺特殊抗原正常的話，具有臨床上重要性的前列腺癌幾乎不存在。反之，肛診及前列腺特殊抗原異常，則前列腺癌的可能性很高，病人必須接受系統性的切片。如其中一種檢查正常而另一種異常時，則經直腸超音波可作為第二線的篩選工具，來決定病人是否需作切片。如依我們提出的診斷流程來決定是否需切片檢查，則必須接受切片檢查病人數會減少很多，但癌症的診斷率卻是相同的。

Digital rectal examination (DRE), transrectal ultrasonography (TRUS) and prostate specific antigen (PSA) are currently widely used in the detection of prostate cancer. In this study, we try to compare these methods and delineate the algorithm for the detection of prostate cancer in the urological practice. Prostate specific antigen values were determined with DAINABOT as-say. Transrectal ultrasonography was performed with an Aloka Model 520. Totally 353 patients receiving prostate biopsy were included in the study. The algorithm was determined by positive predictive value that was calculated from the biopsy data. When two of three diagnostic modalities were normal, the probabilities of detecting cancer were almost negligible. If both of these diagnostic methods were abnormal, it was possible to predict cancer with a higher probability. The combination of DRE and PSA is the best of these two combinations. Systematic biopsy resulted in a nearly two times’ detection rate than directed biopsy. The combination of normal DRE and PSA are abnormal, the probability of prostate cancer is very high. Systematic biopsies should be performed. For other conditions TRUS could be served as a second line screening method to gain the same cancer detection rate but fewer biopsies needed.