Efficacy of Narrow-Band Imaging (NBI), Especially the Second Generation NBI for Adenoma Detection Rate: Systematic Review and Meta-Analysis

Abstract

Introduction: Incidence of interval colorectal cancer (CRC), CRC diagnosed between the time of screening colonoscopy and the scheduled time of surveillance colonoscopy, was reported to be inversely correlated with higher adenoma detection rate (ADR). Image enhanced endoscopy, such as narrow band imaging (NBI) was expected to improve ADR. However, there has been no evidence of significant efficacy of the 1st generation NBI for ADR compared to conventional white light. The 2nd generation NBI was invented with fixing relatively dark image of the 1st generation NBI. The 2nd generation NBI was reported to provide at least two-fold brighter image. The aim of this study was to determine the efficacy of NBI, especially the 2nd generation NBI for ADR. Methods: We performed a comprehensive literature review following Preferred Reporting Items for Systematic reviews and Meta-Analyses from 1966 through July 2016 using appropriate search terms in MEDLINE, EMBASE, and Cochrane library.Inclusion criteria required full literatures published in English and randomized controlled trial (RCT). Heterogeneity was evaluated by I2, pooled estimates were calculated by fixed effects model (FEM) (Mantel-Haenszel method) or random effects model (REM) (DerSimonian and Laird method). The quality of each study was evaluated by randomization sequence and allocation concealment. Publicaton bias or small study effect was checked by funnel plot with Egger's test. Results: Regarding the 1st and 2nd NBI, 21 RCTs including 7442 patients were selected. The 2nd generation NBI was used in three studies. Assuming that relative risk (RR) more than 1 meant significant efficacy of improving ADR compared to conventional white light. Pooled RR [95%CI] of NBI (both 1st and 2nd generation) was 1.03 [0.98-1.09] (I2=0%) (FEM). Pooled RR [95%CI] of the 1st generation NBI and the 2nd generation NBI was 1.20 [0.96-1.08] (I2=0%) (FEM) and 1.12 [0.94-1.33] (I2=61%) (REM), respectively. The validity of allocation sequence and allocation concealment were confirmed in more than half studies. There was no significant publication bias or small study effect. Conclusion: Our study did not show any evidence of significant efficacy of NBI (Both 1st and 2nd generation) for ADR. The 2nd generation NBI improved ADR compared to the 1st generation NBI, but it was not statistically significant. The 2nd generation NBI did not show any significant efficacy for ADR compared to conventional white light, either.