title: A multicenter validation of an endoscopic classification with narrow band imaging for gastric precancerous and cancerous lesions.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Gastroenterology, Portuguese Oncology Institute of Porto, Rua Dr. Bernardino de Almeida, Porto, Portugal.
authors.forename: P
authors.initials: P
authors.lastname: Pimentel-Nunes
authors.forename: M
authors.initials: M
authors.lastname: Dinis-Ribeiro
authors.forename: J B
authors.initials: JB
authors.lastname: Soares
authors.forename: R
authors.initials: R
authors.lastname: Marcos-Pinto
authors.forename: C
authors.initials: C
authors.lastname: Santos
authors.forename: C
authors.initials: C
authors.lastname: Rolanda
authors.forename: R P
authors.initials: RP
authors.lastname: Bastos
authors.forename: M
authors.initials: M
authors.lastname: Areia
authors.forename: L
authors.initials: L
authors.lastname: Afonso
authors.forename: J
authors.initials: J
authors.lastname: Bergman
authors.forename: P
authors.initials: P
authors.lastname: Sharma
authors.forename: T
authors.initials: T
authors.lastname: Gotoda
authors.forename: R
authors.initials: R
authors.lastname: Henrique
authors.forename: L
authors.initials: L
authors.lastname: Moreira-Dias
mesh_terms: D000230:Adenocarcinoma / Q000098:blood supply / Q000145:classification* / Q000473:pathology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D002983:Clinical Competence; D005260:Female; D005753:Gastric Mucosa / Q000098:blood supply / Q000473:pathology; D005756:Gastritis / Q000175:diagnosis / Q000382:microbiology; D005773:Gastroscopy; D016481:Helicobacter Infections / Q000175:diagnosis; D016480:Helicobacter pylori; D006801:Humans; D007089:Image Enhancement; D008027:Light; D008297:Male; D055806:Microvessels / Q000473:pathology; D008875:Middle Aged; D011230:Precancerous Conditions / Q000098:blood supply / Q000145:classification* / Q000473:pathology*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D013274:Stomach Neoplasms / Q000098:blood supply / Q000145:classification* / Q000473:pathology*; D055815:Young Adult