Narrow-band imaging in the diagnosis of deep submucosal colorectal cancers: a systematic review and meta-analysis

Background and aims Magnifying endoscopy with narrow -band imaging (M-NBI) has been widely used in the differential diagnosis of deep subrnucosal colorectal cancers (dSMCs) from superficial submucosal cancers (sSMCs) and intramucosal neoplasms. We aimed to pool the diagnostic efficacy of M-NBI and compare it with that of magnifying chrornoendoscopy (M-CE) in diagnosing colorectal dSMC. Methods PubMed, EMBASE, and the Cochrane Library were searched to identify eligible studies. Meeting abstracts were also searched. A bivariate mixed-effects binary regression model was used in the meta-analysis to calculate the pooled diagnostic efficacy of M-NBI and compare it with that of M-CE in the diagnosis of dSMC. Subgroup analyses and meta-regression were conducted to explore sources of heterogeneity. Results We included 17 studies: 14 full texts and 3 meeting abstracts. The pooled sensitivity, specificity, and area under the summary receiver operating characteristic curve (AUC) with 95% confidence intervals (Os) in diagnosing dSMC were 74% (66 %-81 %; 12=84.6%), 98% (94 %-99%; 12=94.4%), and 0.91 (0.88-0.93), respectively, for M-NBI. The pooled sensitivity, specificity and AUC (95%CI) were 84% (76 %-89 %; I-2=76.9%), 97% (94%-99%; I-2=90.2%), and 0.97 (0.95-0.98), respectively, for M-CE. M-NBI had lower sensitivity (P<0.01) than M-CE with similar specificity (P=0.32). Subgroup analyses and meta-regression indicated that endoscopic diagnostic criteria, study type, endoscope type, risk of index test bias, and histopathological diagnostic criteria might be the sources of heterogeneity. Conclusions M-NBI and M-CE had comparable specificities in diagnosing dSMC, but the sensitivity of M-NBI was slightly lower than that of M-CE.