During the second pass, the cecum was reintubated and the same colonic segment was re-examined with NBI, and additional polyps were photographed and removed. In the back-to-back study

GS-1101 in vitro by East et al. in surveillance for hereditary non-polyposis cancer syndrome (HNPCC) patients, the number of adenomas detected on NBI almost doubled when performed by endoscopists who had experience with at least 100 colonoscopies with NBI.17 In a randomized tandem colonoscopy trial, 276 patients were randomized to undergo colonoscopy using NBI or white-light examination. All patients then underwent a second colonoscopy using white light as the reference standard. There were no significant differences in adenoma miss rates between

the NBI and the white-light techniques (12.6% vs 12.1%).14 In a small pilot study, 47 patients found to have neoplastic lesions during high-definition white-light colonoscopy underwent colonoscopy with NBI. The results of the first examination were blinded from the colonoscopist. NBI detected more lesions, particularly lesions in the right colon and flat lesions than high definition white-light colonoscopy.16 Blinding of endoscopists is not feasible in these studies. The disparity in results from randomized controlled trials and back-to-back studies may be attributed to several factors. Because of the difference in study methodology CHIR-99021 in vivo (Table 1), it is difficult to make direct comparison between tandem studies with the four randomized controlled studies. The use of high-definition monitors for white-light

endoscopy in Rex and Helbig’s study can potentially improve adenoma detection compared with standard monitor. Other confounding factors include differences in NBI systems and experience of colonoscopists. There is likely to be a learning curve with NBI for adenoma detection. 上海皓元医药股份有限公司 Behavior of colonoscopists may also be different when screening high-risk patients with a more thorough examination, particularly when looking for small lesions. Overall, pooled analysis showed that NBI was only marginally better than white-light endoscopy for adenoma detection.18 Patients with longstanding ulcerative colitis have an increased risk of developing colorectal cancer. In the only randomized crossover study of NBI in ulcerative colitis surveillance, NBI was not better than white-light endoscopy in dysplasia detection, although this study utilized an early NBI prototype system that was much darker than those currently available.15 The background inflammation in some patients with inflammatory bowel disease may potentially negate NBI contrast enhancement for hypervascular dysplastic lesions. A more positive report indicated that a third-generation NBI prototype plus magnification could reveal fine superficial vessels with increased diameter and densities as seen in neoplastic lesions compared with normal nucosa.