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Interobserver variability in assessing dysplasia and architecture in colorectal adenomas: a multicentre Canadian study
  1. Allison Osmond1,
  2. Hector Li-Chang2,3,
  3. Richard Kirsch3,
  4. Dimitrios Divaris4,
  5. Vincent Falck5,
  6. Dong Feng Liu6,
  7. Celia Marginean7,
  8. Ken Newell8,
  9. Jeremy Parfitt1,
  10. Brian Rudrick8,
  11. Heidi Sapp9,
  12. Sharyn Smith10,
  13. Joanna Walsh1,
  14. Fasahat Wasty11,
  15. David K Driman1
  1. 1Western University, London, Canada
  2. 2University of British Columbia, Vancouver, British Columbia, Canada
  3. 3University of Toronto, Toronto, Ontario, Canada
  4. 4Grand River Hospital, Kitchener, Ontario, Canada
  5. 5University of Calgary, Calgary, Canada
  6. 6Woodstock General Hospital, Woodstock, Ontario, Canada
  7. 7University of Ottawa, Ottawa, Ontario, Canada
  8. 8Grey Bruce Health Services, Owen Sound, Ontario, Canada
  9. 9Dalhousie University, Halifax, Nova Scotia, Canada
  10. 10Huron Perth Health Alliance, Stratford, Ontario, Canada
  11. 11 St. Thomas Elgin General Hospital, St. Thomas, Ontario, Canada
  1. Correspondence to Dr David K Driman, Department of Pathology, London Health Sciences Centre, 339 Windermere Rd., London Ontario, Canada N6A 5A5; David.Driman{at}


Aims Following the introduction of colorectal cancer screening programmes throughout Canada, it became necessary to standardise the diagnosis of colorectal adenomas. Canadian guidelines for standardised reporting of adenomas were developed in 2011. The aims of the present study were (a) to assess interobserver variability in the classification of dysplasia and architecture in adenomas and (b) to determine if interobserver variability could be improved by the adoption of criteria specified in the national guidelines.

Methods An a priori power analysis was used to determine an adequate number of cases and participants. Twelve pathologists independently classified 40 whole-slide images of adenomas according to architecture and dysplasia grade. Following a wash-out period, participants were provided with the national guidelines and asked to reclassify the study set.

Results At baseline, there was moderate interobserver agreement for architecture (K=0.4700; 95% CI 0.4427 to 0.4972) and dysplasia grade (K=0.5680; 95% CI 0.5299 to 0.6062). Following distribution of the guidelines, there was improved interobserver agreement in assessing architecture (K=0.5403; 95% CI 0.5133 to 0.5674)). For dysplasia grade, overall interobserver agreement remained moderate but decreased significantly (K=0.4833; 95% CI 0.4452 to 0.5215). Half of the cases contained high-grade dysplasia (HGD). Two pathologists diagnosed HGD in ≥75% of cases.

Conclusions The improvement in interobserver agreement in classifying adenoma architecture suggests that national guidelines can be useful in disseminating knowledge, however, the variability in the diagnosis of HGD, even following guideline review suggests the need for ongoing knowledge-transfer exercises.

  • Colorectal Cancer
  • Colon
  • GI Neoplasms

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