Background and study aim: The reliability and external validity of narrow band imaging (NBI) in the stomach have not been described consistently. The aim of the current study was to describe and estimate the accuracy and reliability of a simplified classification system for NBI in the diagnosis of gastric lesions.
Methods: Consecutive patients undergoing NBI endoscopy at two reference centers (n=85, 33% with dysplasia) were included in two studies. In total, 224 different areas were biopsied and recorded onto video. In the derivation study, previously described NBI features were analyzed in order to develop a simplified classification. In the validation study the accuracy and reliability of this classification were estimated among three groups of endoscopists with different levels of expertise in NBI.
Results: The reliability/accuracy results from the derivation study allowed the creation of a simplified NBI classification. In the validation study, "regular vessels with circular mucosa" (pattern A) was associated with normal histology (accuracy 83%; 95% confidence interval [CI] 75 %-90%); "tubulo-villous mucosa" (pattern B) was associated with intestinal metaplasia (accuracy 84%; 95CI 77%-91%; positive likelihood ratio [LR+]=4.75); and "irregular vessels and mucosa" (pattern C) was associated with dysplasia (accuracy 95%; 95CI 90%-99%; LR+=44.33). The reproducibility of these patterns was high (k=0.62). "Light-blue crest" was moderately reliable (k=0.49) but specific (87%) for intestinal metaplasia. A variable vascular density (additional pattern+) was the best feature for Helicobacter pylori gastritis (accuracy 70%; 95CI 59%-80%) but showed only fair reliability (k=0.38). Non-experienced endoscopists presented lower agreement (k=0.6 vs. k=0.75) and accuracy (74% vs. 86%) than international experts/experienced endoscopists.
Conclusion: A simplified NBI classification is accurate and reliable for the diagnosis of intestinal metaplasia and dysplasia. The classification should be further assessed and validated on a per-patient assessment of NBI, and by comparing NBI with other imaging technologies.
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