UBC is still the most common malignancy of the urinary tract in both male and female and cystoscopy currently is believed to be the optimal approach for the detection and monitoring of both primary tumor and follow-up of patient after resection [15]. Nevertheless, the false negative results associated with cystoscopy can range from 10 to 40% [16], thus in this study, we included 1021 patients who had diagnosed with primary UBC and analyzed their 2 years follow-up data to assess the optimal diagnostic tool for diagnosing recurrent UBC. By using the cystoscopy results as gold standard, we compared the diagnostic accuracy of B ultrasound in bladder, DAPK methylation in urinary sediment, urinary cytology and combination of B ultrasound in bladder with DAPK methylation in urinary sediment. The findings in our study supported that the combination of B ultrasound in bladder with detection of DAPK methylation in urinary sediment has a high performance in diagnosing recurrent UBC.
The initial finding in our study showed that the detection of B ultrasound in the bladder has highly consistent results with that of cystoscopy, which in certain way proved that ultrasonography may also be a reliable way to diagnose UBC. This study also found that the AUC of ultrasonography was 0.854 with a sensitivity of 71.43% and a specificity of 99.04%. This is in accordance with observations in a other study that modern sensitive transducers have made much improvement on the imaging of urinary tract rendering transabdominal ultrasonography (US) in visualizing intraluminal filling defects in the bladder than it was in the past [17]. Frankly, it has to be admitted that although ultrasonography represents a valuable surveillance tool in UBC diagnosis, its accuracy is still behind that of cystoscopy. There are many factors that may affect the accuracy of UBC diagnosis, including operator’s skill, amount of abdominal fat and bladder distension during procedure. So, ultrasonography may prove a useful adjunct to cystoscopy as a screening test for UBC.
Methylation of tumor suppressor gene promoter leads to transcription inactivation and is involved in tumorigenesis [14]. DAPK gene is closely associated with cancer genesis by inducing the suppression of cell proliferation and the product of DAPK gene is considered to be a positive mediator of apoptosis [18, 19]. In a previous study, the percentage of DAPK methylation in UBC patients was 64.3% [18]. In this study, we detect the DAPK promoter methylation in urinary sediment in included UBC patients. ROC curve demonstrated that the AUC for DAPK methylation was 0.840, sensitivity of 75.71, specificity of 92.22 and YI of 0.679. Moreover, in this study, the detection of ultrasonography was also analyzed with combination of DAPK methylation in urinary sediment, and the AUC, sensitivity, specificity and YI of the combination were all the greatest among all the applied approaches, respectively of 0.922, 92.86%, 91.63% and 0.845. Those results supported that the combination of ultrasonography with DAPK methylation detection was superior to other single approach.
We also assess the performance of urinary cytology in diagnosing UBC and the results were far less than ultrasonography and DAPK methylation detection. The ROC showed that the AUC was only 0.693, sensitivity of 38.57%, but with a high specificity of 100%. This observation was consistent with previous description thatcytology, however, remains the preferred bladder tumor marker for specificity [20].