• colorectal cancer screening;
  • colorectal polyps;
  • histological diagnosis;
  • interobserver variation

van Putten P G, Hol L, van Dekken H, Han van Krieken J, van Ballegooijen M, Kuipers E J & van Leerdam M E (2011) Histopathology 58, 974–981 Inter-observer variation in the histological diagnosis of polyps in colorectal cancer screening

Aim:  To determine the inter-observer variation in the histological diagnosis of colorectal polyps.

Methods and 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.