Background and aims: Histological remission [HR] is a potential treatment target in ulcerative colitis [UC]. Limited 'real world' data are available on the reliability of histological scoring when assessing minimal histological inflammation. The aim of this study was to investigate the reliability of UC histological scores in colonic biopsies showing mucosal healing [MH] and limited histological inflammation, and to compare the 'daily practice' histological assessment with expert reviews by gastrointestinal [GI] pathologists.
Methods: We performed a retrospective single-centre study. Colonic biopsies from UC patients with MH [Mayo score ≤ 1] were included. All biopsies assessed in daily practice were reassessed by three blinded GI pathologists using three histological scores (Geboes score [GS], Riley score [RS], Harpaz [Gupta] Index [HGI]) and a global visual scale [GVS]. We evaluated inter- and intra-observer variation between GI pathologists and correlations between scores including the initial histological assessment using Cronbach's alpha and Spearman rho analysis.
Results: In total, 270 biopsies from 39 UC patients were included. The inter-observer concordance for all histological indexes was substantial to almost perfect [GS 0.84; HGI 0.61; GVS 0.74, RS 0.91]. Correlation between the RS and GS was almost perfect [R = 0.86], but we found no correlation between the primary histological assessment and reassessment by GI pathologists.
Conclusions: Current UC histological scores reliably assess limited histological inflammation in UC patients. The discrepancy between the initial histological assessment and the reassessment by dedicated GI pathologists suggests a gap between daily practice and academic expertise. This issue may limit the implementation of HR as a treatment target for UC in daily practice.