Inter-observer reliability of methods to determine complete resection of adenomatous polyps ≤20 mm in colonoscopy.

Background and Aims: Forceps margin biopsy and polypectomy specimen margins have been used to assess for polypectomy resection adequacy. Inter-observer reliability of both methods has not been well described. Patients and Methods: Interpretability of polypectomy specimens for the presence of residual neoplasia at the margin was assessed by two blinded pathologists. Next, concordance of forceps margin biopsies interpretations between three blinded pathologists was evaluated by calculation of inter-observer kappa. Results: Rates of polypectomy specimen margin interpretability were low, 24/92 (26%) pathologist A, and 28/92 (30.4%) pathologist B. Concordance of forceps margin biopsies interpretations (n=129) between pathologists was high. Two internal pathologists showed substantial agreement in margin biopsy interpretations (kappa 0.779, 95% CI 0.543, 0.912). The concordance remained strong after biopsies were reviewed by a third external pathologist (kappa score 0.829, 95% CI 0.658, 0.924). There was complete agreement on 123/129 (95.3%) for presence of neoplasia between all three pathologists. Conclusion: The majority of polypectomy specimen margins were uninterpretable by pathologists for the presence of residual neoplasia. Forceps margin biopsy shows strong inter-observer reliability in adenomatous lesions.