title: Inter-observer variation in the histological diagnosis of polyps in colorectal cancer screening.
abstract: OBJECTIVE
  To determine the inter-observer variation in the histological diagnosis of colorectal polyps.
  
  
  RESULTS
  Four hundred and forty polyps were randomly selected from a colorectal cancer screening programme. Polyps were first evaluated by a general (324 polyps) or expert (116 polyps) pathologist, and subsequently re-evaluated by an expert pathologist. Conditional agreement was reported, and inter-observer agreement was determined using kappa statistics. In 421/440 polyps (96%), agreement for their non-adenomatous or adenomatous nature was obtained, corresponding to a very good kappa value of 0.88. For differentiation of adenomas as non-advanced and advanced, consensus was obtained in 266/322 adenomas (83%), with a moderate kappa value of 0.58. For the non-adenomatous or adenomatous nature, both general and expert pathologists, and expert pathologists between each other, showed very good agreement {kappa values of 0.89 [95% confidence interval (CI) 0.83-0.95] and 0.86 (95% CI 0.73-0.98), respectively}. For categorization of adenomas as non-advanced and advanced, moderate agreement was found between general and expert pathologists, and between expert pathologists [kappa values of 0.56 (95% CI 0.44-0.67) and 0.64 (95% CI 0.43-0.85), respectively].
  
  
  CONCLUSIONS
  General and expert pathologists demonstrate very good inter-observer agreement for differentiating non-adenomas from adenomas, but only moderate agreement for non-advanced and advanced adenomas. The considerable variation in differentiating non-advanced and advanced adenomas suggests that more objective criteria are required for risk stratification in screening and surveillance guidelines.
authors.affiliation: Department of Gastroenterology and Hepatology, Erasmus University Medical Centre, Rotterdam, The Netherlands. p.g.vanputten@erasmusmc.nl
authors.forename: Paul G
authors.initials: PG
authors.lastname: van Putten
authors.forename: Lieke
authors.initials: L
authors.lastname: Hol
authors.forename: Herman
authors.initials: H
authors.lastname: van Dekken
authors.forename: J
authors.initials: J
authors.lastname: Han van Krieken
authors.forename: Marjolein
authors.initials: M
authors.lastname: van Ballegooijen
authors.forename: Ernst J
authors.initials: EJ
authors.lastname: Kuipers
authors.forename: Monique E
authors.initials: ME
authors.lastname: van Leerdam
mesh_terms: D000236:Adenoma / Q000175:diagnosis* / Q000453:epidemiology / Q000473:pathology*; D000368:Aged; D003111:Colonic Polyps / Q000175:diagnosis* / Q000453:epidemiology / Q000473:pathology*; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000453:epidemiology / Q000473:pathology*; D003937:Diagnosis, Differential; D005243:Feces; D006801:Humans; D007150:Immunohistochemistry; D008403:Mass Screening / Q000379:methods*; D008875:Middle Aged; D015588:Observer Variation; D009780:Occult Blood; D012812:Sigmoidoscopy