A prospective comparative study of narrow-band imaging, chromoendoscopy, and conventional colonoscopy in the diagnosis of colorectal neoplasia

Abstract

Background: Discrimination between neoplastic and non-neoplastic lesions is crucial in colorectal cancer screening. Application of narrow-band imaging (NBI) in colonoscopy visualises mucosal vascular networks in neoplastic lesions and may improve diagnostic accuracy. Aim: To compare the diagnostic efficacy of NBI in differentiating neoplastic from non-neoplastic colorectal lesions with diagnostic efficacies of standard modalities, conventional colonoscopy, and chromoendoscopy. Methods: In this prospective study, 180 colorectal lesions from 133 patients were observed with conventional colonoscopy, and under low-magnification and high-magnification NBI and chromoendoscopy. Lesions were resected for histopathological analysis. Endoscopic images were stored electronically and randomly allocated to two readers for evaluation. Sensitivity, specificity and diagnostic accuracy of each endoscopic modality were assessed by reference to histopathology. Results: NBI and chromoendoscopy scored better under high magnification than under low magnification in comparison with conventional colonoscopy. The diagnostic accuracy of NBI with low or high magnification was significantly higher than that of conventional colonoscopy (low magnification: p = 0.0434 for reader 1 and p = 0.004 for reader 2; high magnification: p,0.001 for both readers) and was comparable to that of chromoendoscopy. Conclusion: Both low-magnification and high-magnification NBI were capable of distinguishing neoplastic from non-neoplastic colorectal lesions; the diagnostic accuracy of NBI was better than that of conventional colonoscopy and equivalent to that of chromoendoscopy. The role of NBI in screening colonoscopy needs further evaluation. M ost of the colorectal cancers (CRCs) arise from preexisting adenomas and such an adenoma-carcinoma sequence provides an opportunity for screening and prevention of CRC.1 Accumulating evidence has indicated that early detection and removal of colorectal adenomas may greatly reduce the mortality and incidence of CRC, and reliable detection and resection of colorectal adenomas before they become malignant has a pivotal role in CRC screening. 2 In the diagnosis of colorectal neoplasia, it is crucial to discriminate neoplastic lesions, including adenomas with dysplasia and invasive cancer, from non-neoplastic ones such as hyperplastic polyps to avoid overlooking neoplastic lesions and the risk of overtreatment. However, using conventional videoendoscopy, it is difficult to differentiate between neoplastic and nonneoplastic lesions and several new diagnostic modalities and endoscopic techniques have been developed to provide more precise diagnosis. Furthermore, previous studies have reported that the average size of depressed advanced lesions (high-grade dysplasia and cancer) is considerably smaller than that of polypoid lesions, showing that lesions should not be excluded based on small size. In chromoendoscopy, a biocompatible dye, such as indigo carmine, can strengthen the surface structure of epithelial lesions. Magnify...

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