Narrow-band imaging with magnification in Barrett's esophagus: validation of a simplified grading system of mucosal morphology patterns against histology

Background and study aims: Validation of a simplified classification of mucosal morphology in prediction of histology in Barrett's esophagus using narrow-band imaging with magnification (NBI-Z) and assessing its reproducibility by endoscopists experienced in the use of NBI (NBI-experts) and by endoscopists who were new to NBI (non-NBI-experts). Patients and methods: In a prospective cohort study of 109 patients with Barrett's esophagus at a single tertiary referral center, mucosal patterns visualized in Barrett's esophagus on NBI-Z were classified into four easily distinguishable types: A, round pits with regular microvasculature; B, vinous/ridge pits with regular microvasculature; C, absent pits with regular microvasculature; D, distorted pits with irregular microvasculature. The NBI-Z grading was compared with the final histopathological diagnosis, and positive (PPV) and negative predictive values (NPV) were calculated. The reproducibility of the grading was then assessed by NBI-expert and non-NBI-expert endoscopists, and interobserver and intraobserver agreement were calculated using x statistics. Results: Per-biopsy analysis: In 903 out of 1021 distinct areas (87.9%) the NBI-Z grading corresponded to the histological diagnosis. Per-patient analysis: The PPV and NPV for type A pattern (columnar mucosa without intestinal metaplasia) were 100 % and 97 % respectively; for types B and C (intestinal metaplasia) they were 88 % and 91 % respectively, and for type D (high-grade dysplasia) 81 % and 99 % respectively. Inter- and intraobserver agreement: The mean K values in assessing the various patterns were 0.71 and 0.87 in the non-expert group; 0.78 and 0.91 in the expert group. Conclusions: This study has validated a simplified classification of the various morphologic patterns visualized in Barrett's esophagus and confirmed its reproducibility when used by NBI-expert and non-NBI-expert endoscopists.