Is Narrow Band Imaging Superior to High-definition White Light Endoscopy in the Assessment of Diminutive Colorectal Polyps?

Rajvinder Singh; Yasser Maqbool Bhat; Prem Harichander Thurairajah; Mohit Pramod Shetti; Mahesh Jayanna; Garry Nind; William Tam; Russell Walmsey; Micheal Bourke; Alan Moss; Robert Chen; Peter Bampton; Ian Roberts-Thomson; Mark Schoeman; Graeme Tucker


J Gastroenterol Hepatol. 2013;28(3):472-478. 

In This Article

Abstract and Introduction


Background and Aim: Diminutive polyps measuring ≤ 5 mm in size constitute 80% of polyps in the colon. We prospectively assessed the performance of high-definition white light endoscopy (hWLE) and narrow band imaging (NBI) in differentiating diminutive colorectal polyps.

Methods: In this prospective, multicenter study, videos of 50 diminutive polyps (31 hyperplastic, 19 adenomatous) in hWLE followed by NBI (total 100 videos) were initially obtained and placed in random order into five separate folders (each folder 20 videos). Eight endoscopists were then invited to predict the histology (each endoscopist 100 videos, 800 video assessments in all). Polyps were classified into types 1–3 (hyperplastic) and type 4 (adenoma). Feedback on individual performance was given after each folder (20 videos) was assessed.

Results: The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy in differentiating hyperplastic from adenomatous polyps by hWLE (400 videos) and NBI (400 videos) were 67.8%, 90.7%, 81.7%, 82.1%, and 82.0%; and 82.2%, 81.5%, 73.1%, 88.2%, and 81.8%, respectively. In the pretest and post-test analysis, the accuracy with NBI improved markedly from 68.8% to 91.3% (P = 0.001) compared with hWLE, 76.3–78.8% (P = 0.850). Overall, the interobserver agreement was 0.46 for hWLE (moderate) and 0.64 for NBI (good).

Conclusions: NBI was as accurate as hWLE in differentiating diminutive colorectal polyps. Once a learning curve was reached, NBI achieved significantly higher accuracies with good interobserver agreement. Using a simplified classification, a didactic learning session and feedback on performance, diminutive colorectal polyps could be predicted with high accuracies with NBI.


Colorectal cancer (CRC) is the second most common cause of cancer death in developed countries.[1] Screening and surveillance has been advocated aggressively in the effort to reduce mortality associated with CRC. The majority of polyps arise from pre-existing adenomas,[2] and current practice guidelines suggest removing all polyps detected during colonoscopy to disrupt the adenoma-carcinoma sequence. Polyps are detected in 40% of screening colonoscopies, and more than 90% are smaller than 1 cm. Of these, 80% are diminutive (≤ 5 mm) in nature and as many as 50% non-neoplastic.[1,3] Polypectomy performed on these polyps are not only time-consuming and associated with complications but does add unnecessary burden and cost when interpreting them. Accurate assessment in vivo that allows differentiating neoplastic and non-neoplastic polyps could not only potentially increase efficiency and avoid complications but may lead to cost savings by as much as 77%.[1]

A number of imaging modalities have been developed recently that enables the differentiation of colorectal polyps in vivo.[4] Most of these techniques however require sophisticated or expensive instrumentation and technical expertise. More so, some are not readily available yet and seem to be confined to research and academic centers. Narrow band imaging (NBI) with optical magnification has proven to be accurate in differentiating adenomatous from hyperplastic colorectal polyps in numerous studies.[5–13] This technology is however not available for widespread use. Colonoscopy with high-definition white light endoscopy (hWLE) and NBI without optical magnification is presently available for routine use. High definition aids in the discrimination of detail, while NBI enhances visualization of tissue vasculature and surface structure. The aim of this study was to evaluate these two technologies in differentiating diminutive polyps to assess if there is a presence of a learning curve and to evaluate interobserver agreement with a group of endoscopists who have had very little or no exposure to NBI.