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Treating beyond endoscopic remission, aiming for histological remission, has shown to reduce relapse and hospitalization rates in patients with ulcerative colitis (UC). However, very little is known on how histological remission associates with patient reported outcomes (PROMs).

PROMs (Simple clinical colitis activity index [SCCAI], IBD disk and Visual Analogue Scales [VAS]) were prospectively collected through a digital questionnaire in all patients with UC undergoing colonoscopy between July 21^st 2020-Jan 21^st 2021. Mayo endoscopic sub score and UCEIS were determined, as well as the Nancy histologic index (NHI) of the most affected area. Endoscopic remission was defined as Mayo endoscopic sub score 0 and UCEIS 0; histologic remission as NHI 0, absence of active inflammation as NHI ≤ 1. PRO2 remission was defined as stool frequency ≤ 1 (absolute stool frequency ≤ 3 OR 1-2 stools more than usual) and rectal bleeding score of 0.

Fifty-six paired assessments were collected in 48 unique patients (Table 1), with a histologic, endoscopic and PRO-2 remission rate of 23.2%, 28.6% and 38.2% respectively. Patients with histologic remission or absence of histologic inflammation had a significantly lower overall IBD disability (p=0.007, p=0.003) and disease activity score (p=0.003, p<0.001), as compared to patients without. In line, NHI correlated with the overall IBD disk (r=0.40, p=0.002) and SCCAI score (r=0.50, p<0.001). Many individual components of both scores (abdominal pain, arthralgia, impact on education and work/interpersonal interactions/sexual function, regulation of defecation, blood loss, general wellbeing, joint pain, numbers of stools during night/day, urgency) differed significantly between patients with and without histologic remission. VAS scores assessing general wellbeing (r=0.33, p=0.01), impact on daily activities (r=0.41, p=0.002), UC-related symptoms (r=0.42, p=0.001) and worries (r=0.40, p=0.002) correlated with histology.  Quartile analysis of the overall IBD disk and SCCAI scores confirmed the highest likelihood for histologic remission in patients with the lowest scores (Q1-Q2 vs Q3-Q4 39.3% vs 7.1%, p=0.01; 40.0% vs 9.7%, p=0.01) (Figure 1). Nevertheless, the overall accuracy of the IBD disk (0.75) or SCCAI score (0.76) for histologic remission is lower (p<0.05) than the accuracy of the Mayo endoscopic (0.90) or UCEIS (0.90) score.

Table 1 : Baseline features

In patients with UC, PROMs for disability and clinical disease activity reflect histologic disease activity and should therefore be further explored in (trial) endpoint discussions. However, they cannot fully replace endoscopic and histologic findings, and should be considered complementary.