Colonoscopy, tumors, and inflammatory bowel disease

A randomized tandem colonoscopy trial of narrow band imaging versus white light examination to compare neoplasia miss rates (Kaltenbach et al., Gut 2008 [1])

This single-center study from the USA examined the ability of narrow band imaging (NBI), a novel “blue light” advanced endoscopic imaging technique, to reduce adenoma miss rates and thereby increase detection. The study was performed in a back-to-back fashion using wide angle (170°) colonoscopes. With the advent of national bowel cancer screening programs and competing technologies such as computed tomography (CT) colonography, the issue of colonoscopic miss rates has been recently highlighted. This has led to a focus on colonoscopic quality, as assessed by adenoma detection rates [2]. This study showed that NBI did not reduce the miss rate. The overall miss rate was 12.3 % (95 % confidence interval [CI] 8.7 – 16.8) for adenomas of all sizes; one 10-mm tubular adenoma was missed but no carcinomas were missed. Nor did NBI significantly increase adenoma detection, with 50 % of patients having at least one adenoma detected with NBI versus 44 % with white light.

Overall miss rates were lower than previously reported in a recent systematic review of back-to-back studies, which reported a 22 % miss rate for adenomas of all sizes (95 %CI 15 – 32) [3]. However, a recently reported European multicenter study (11 centers, 294 patients) showed a miss rate of 20 % for adenomas of all sizes, and more concerning, 11 % for advanced adenomas, suggesting miss rates remain a problem [4]. The results for NBI detection are consistent with three other randomized studies assessing NBI for adenoma detection, none of which showed a significant increase in adenoma detection with NBI in routine patients ([Table 1]). With four studies now reported totaling 1349 patients, it seems unlikely that NBI will result in large increases in adenoma detection compared with well-performed white light examination. Combining the results of these four studies suggests a modest, but nonsignificant, absolute benefit for adenoma detection of 3.7 % (95 %CI –1.6 – + 9.0), risk [benefit] ratio 1.09 [95 %CI 0.96 – 1.23]), meaning that 27 patients would need to be examined with NBI to detect one additional patient with an adenoma. Given these results, it seems unlikely that NBI will be the whole solution to adenoma miss rates, at least in routine patients.

White light adenoma detection rates were very high in three of the four studies (34 % – 67 %) suggesting that white light colonoscopy performed with optimized technique can be very effective in the detection of adenomas. Perhaps one message is that if endoscopists go back-to-basics for withdrawal technique (i. e. slow examination on withdrawal [≥ 6 minutes]; adequate luminal distension [insufflation, patient position changes, anti-spasmodics]; re-examining flexures and folds; and meticulous clearing of fluid pools [8]), miss rates are low and detection rates can be high with white light alone. Optimized withdrawal technique remains a pre-requisite for endoscopists embarking on advanced imaging technologies.

Table 1 Patients with at least one adenoma detected in randomized studies of narrow band imaging versus white light colonoscopy. Study [ref.] No. of patients No. of patients with at least one adenoma detected (%) P-value NBI White light Rex et al., Gastroenterology 2007 5 434 140/217 (64.5) 145/217 (66.8) 0.61 Adler et al., Gut 2008 6 396 45/198 (22.7) 33/198 (16.7) 0.13 Inoue et al., J Gastroenterology 2008 7 243 51/122 (41.8) 41/121(33.8) 0.20 Kaltenbach et al., Gut 2008 1† 276 68/135 (50) 62/141 (44) 0.29 Total 1349 304/672 (45.2) 281/677 (41.5) 0.17* NBI, narrow band imaging. *Chi-squared test. †Calculated from percentages in the manuscript.

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