Interobserver reliability of the Nancy index for ulcerative colitis: An assessment of the practicability and ease of use in a single-centre real-world setting.


Huy Duc Le, Theresa Pflaum, Johannes Labrenz, Soner Sari, Fabienne Bretschneider, Florian Tran, Arne Lassen, Susanna Nikolaus, Silke Szymczak, Diana Kormilez, Philip Rosenstiel, Stefan Schreiber, Konrad Aden, Christoph Röcken

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Histological disease severity assessment in ulcerative colitis (UC) has become a mainstay in clinical endpoints definition (“histologic remission”) in clinical trials of UC. Several scores are established in the microscopical assessment of disease activity, but the Nancy index (NI) stands out being a histological index with the least amount of scoring items among these scores. To which extent histologic assessment using NI is affected by interobserver reliability in a real word setting, is poorly understood. We therefore performed a single-center retrospective analysis of NI assessment in patients with UC.


We retrospectively evaluated the NI in two independent cohorts (total: 1085 biopsies, 547 UC patients) of clinically diagnosed UC patients, who underwent colonoscopy between 2007 and 2020. Cohort #1 consisted of 637 biopsies from 312 patients, Cohort #2 consisted of 448 biopsies from 235 patients. Two blinded pathologists with different levels of expertise scored all biopsies of each cohort. A consensus conference was held for cases with discrepant scoring results. Finally, an overall consensus scoring was obtained from both cohorts.


The interobserver-agreement of the NI was substantial after the assessment of 1085 biopsy samples (κ = 0.796 [95%-CI: 0.771-0.820]). An improvement of the interobserver-agreement was found with growing numbers of samples evaluated by both observers (Cohort #1: κ = 0.772 [95%-CI: 0.739-0.805]; Cohort #2: κ = 0.829 [95%-CI: 0.793-0.864]). The interobserver discordance was the highest in NI grade 1 (observer 1: n=128; observer 2: n=236). Interobserver discordance was the lowest in NI grades 0 (observer 1: n=504; observer 2: n=479) and 3 (observer 1: n=71; observer 2: n=66).


The NI is an easy-to-use index with high interobserver reliability to assess the histological disease activity of UC patients in a real-world setting. While NI grades 0 and 3 had a high level of agreement between the observers, NI grade 1 had a poorer agreement-level. This highlights the clinical need to specify histological characteristics leading to NI grade 1.