The AI-based Red Density score is correlated with the established and new histological indices for ulcerative colitis in an independent cohort

Aims Red Density (RD) is an automated endoscopic tool that is developed for the objective evaluation of disease activity in ulcerative colitis (UC). Initial development was based on an algorithm including histological disease activity based on Robarts histological index (RHI). New histological scores for UC have been developed since. We aimed to establish the correlation between RD and the Nancy histological index (NHI) and PICaSSO Histologic Remission Index (PHRI).

Methods Patients included in 4 centers in the ongoing PROCEED-UC study (NCT04408703) had assessment with RD in the rectum and sigmoid at baseline, week 52 or early termination visit. RD score ranges between 0 and 255, cut-off for remission was previously determined to be<60.[1] Biopsies were taken according to protocol and scored for the Geboes score (GBS), RHI, NHI, PHRI in a blinded way after initial scoring convention training. Correlation was tested on patient level between mean RD per segment and the different histological indices based on Spearman correlation.

Results Ninety-six patients from 4 centers were included representing 2634 RD images from 400 colonic segments with biopsies and corresponding RD score. Mean (±SEM) rectal RD score was 32.7 (±4.54), 33.69 (±5.25) and 64.86 (±31.71) at baseline, w52 and ET, respectively. Mean sigmoidal RD score was 38.13 (±3.68), 42.82 (±11.80) and 77.33 (±24.65) at baseline, week 52 and ET, respectively. There was a significant correlation between the highest mean RD score per patient and the NHI (r=0.60, p<0.0001) and the PHRI (r=0.62, p<0.0001). In the rectum the RD score at all time points correlated significant with NHI (r=0,53, p<0.0001) and PHRI (r=0.63, p<0.0001). Similar correlation was seen in the sigmoid for NHI (r=0.51, p<0.0001) and PHRI (r=0.22, p0.0108). A RD score of<57.5 (AUC 0.7820 (95CI 0.7047 – 0.8593), p<0.0001) was associated with histological remission based on NHI (<2) and a RD score of<64.5 (AUC 0.8133 (95% CI 0.7053 – 0.9212), p<0.0001) with histological remission based on PHRI (=0). The current dataset demonstrated to be stable in line with the previously established RD cut-off with GBS and RHI. [1]

Conclusions In an independent cohort of patients with UC the correlation with the established and new histological indices is confirmed. This confirms the value of RD as objective endoscopic tool for the assessment of histological and endoscopic disease activity.

Publication History

Article published online:
15 April 2024

• References

• 1 Bossuyt P, Nakase H, Vermeire S, De G, Eelbode T, Ferrante M. et al. Automatic, computer-aided determination of endoscopic and histological inflammation in patients with mild to moderate ulcerative colitis based on red density. Gut 2020; 69: 1778-86