title: Interlaboratory variability in the grading of dysplasia in a nationwide cohort of colorectal adenomas.
abstract: OBJECTIVE
  Although high-grade dysplasia (HGD) is a risk factor for malignant transformation and the future development of adenomas/carcinomas, grade is not incorporated in the Dutch guidelines for colonoscopy surveillance, partly because of presumed interobserver variability. The aim of this study was to analyse, in a nationwide cohort of colorectal adenomas, the interlaboratory variability in the grading of dysplasia in daily practice.
  
  
  RESULTS
  From the Dutch Pathology Registry, all synoptically reported classic adenomas in The Netherlands in 2013 were identified. The proportion of adenomas with HGD was determined for biopsies and polypectomies, and compared between 37 laboratories by the use of multivariable logistic regression analyses. In total, 21 030 colonoscopies of 20 270 patients were included. HGD was reported in 530 (3.6%) of 14 866 adenomas diagnosed on biopsies (range between laboratories: 0-13.6%) and in 983 (11.8%) of 8346 adenomas diagnosed on polypectomies (range: 3.1-42.9%). After adjustment for case mix, 13 (35%) laboratories reported a significantly lower or higher frequency of HGD than average.
  
  
  CONCLUSIONS
  We observed considerable interlaboratory variation in the grading of dysplasia in colorectal adenomas, which could be only partly explained by differences in case mix. Therefore, better standardization of grading criteria is needed before grade of dysplasia can usefully be incorporated in colonoscopy surveillance guidelines.
authors.affiliation: Department of Pathology, University Medical Centre Utrecht, Utrecht, The Netherlands.|Foundation PALGA (the Nationwide Network and Registry of Histo- and Cytopathology in The Netherlands), Houten, The Netherlands.|Symbiant Pathology Expert Centre, Alkmaar, The Netherlands.
authors.forename: Chantal C H J
authors.initials: CC
authors.lastname: Kuijpers
authors.affiliation: Foundation PALGA (the Nationwide Network and Registry of Histo- and Cytopathology in The Netherlands), Houten, The Netherlands.|Department of Pathology, Radboud University Medical Centre, Nijmegen, The Netherlands.
authors.forename: Caro E
authors.initials: CE
authors.lastname: Sluijter
authors.affiliation: Department of Pathology, Erasmus Medical Centre, Rotterdam, The Netherlands.|NVVP (Dutch Society of Pathology), Utrecht, The Netherlands.
authors.forename: Jan H
authors.initials: JH
authors.lastname: von der Thüsen
authors.affiliation: NVVP (Dutch Society of Pathology), Utrecht, The Netherlands.|Department of Pathology, VU University Medical Centre, Amsterdam, The Netherlands.
authors.forename: Katrien
authors.initials: K
authors.lastname: Grünberg
authors.affiliation: Foundation PALGA (the Nationwide Network and Registry of Histo- and Cytopathology in The Netherlands), Houten, The Netherlands.|Department of Medical Oncology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Martijn G H
authors.initials: MG
authors.lastname: van Oijen
authors.affiliation: Department of Pathology, University Medical Centre Utrecht, Utrecht, The Netherlands.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: van Diest
authors.affiliation: Department of Pathology, University Medical Centre Utrecht, Utrecht, The Netherlands.|Symbiant Pathology Expert Centre, Alkmaar, The Netherlands.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Jiwa
authors.affiliation: Foundation PALGA (the Nationwide Network and Registry of Histo- and Cytopathology in The Netherlands), Houten, The Netherlands.|Department of Pathology, Radboud University Medical Centre, Nijmegen, The Netherlands.
authors.forename: Iris D
authors.initials: ID
authors.lastname: Nagtegaal
authors.affiliation: Foundation PALGA (the Nationwide Network and Registry of Histo- and Cytopathology in The Netherlands), Houten, The Netherlands.
authors.forename: Lucy I H
authors.initials: LI
authors.lastname: Overbeek
authors.affiliation: Department of Pathology, University Medical Centre Utrecht, Utrecht, The Netherlands.|Foundation PALGA (the Nationwide Network and Registry of Histo- and Cytopathology in The Netherlands), Houten, The Netherlands.
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Willems
mesh_terms: D000236:Adenoma / Q000145:classification*; D000368:Aged; D001706:Biopsy; D002277:Carcinoma / Q000145:classification*; D015331:Cohort Studies; D003111:Colonic Polyps / Q000145:classification*; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000145:classification*; D005260:Female; D006801:Humans; D006965:Hyperplasia / Q000145:classification; D008297:Male; D009426:Netherlands; D015588:Observer Variation; D012307:Risk Factors; D011795:Surveys and Questionnaires
keywords: colorectal adenoma; dysplasia; grading; histopathology; variability