P302 Serum IL-6 is associated with treatment refractoriness in acute severe ulcerative colitis

Background Response to therapy in acute severe ulcerative colitis (ASUC) is highly variable ranging from steroid response to salvage therapy failure and emergency colectomy. Biomarkers that accurately predict outcomes in ASUC early in the admission may help improve its management. We aimed to ascertain whether peripheral serum cytokine levels on admission correlate with refractoriness to medical therapy. Methods Peripheral blood was collected from 34 subjects, including 29 patients with ASUC on admission (baseline) and 5 healthy controls. All patients with ASUC received intravenous steroids, with those refractory to steroids going on to receive infliximab (IFX) salvage. Eight cytokines were measured at baseline using a multiplexed cytokine assay (Bio-Rad). Clinical response to steroids and/or to the first IFX dose was assessed and used to classify patients based on increasing order of disease refractoriness (steroid-responders, IFX-responders and IFX non-responders). These groups were then evaluated to check for correlations with baseline cytokine levels. Results Our cohort consisted of steroid responders (n=9), IFX responders (n=12) and IFX non-responders (n=8). Median serum IL-6 level was 1.6 pg/mL (IQR:1.6-2.1) in healthy controls compared to 2.7 pg/mL (IQR:1.4-6.3) in ASUC (p=0.3). In patients with ASUC, there was a positive correlation between IL-6 and treatment refractoriness (Spearman’s correlation [rs]=0.56, p=0.002). Compared with steroid responders (1.36 pg/mL), serum IL-6 was significantly higher in both IFX responders and IFX non-responders (3.44 and 5.50 pg/mL, p=0.02 and p=0.009 respectively) (Fig 1). Patients with ASUC had higher serum IL-8 compared to healthy controls (17.8 vs 6.9 pg/mL, p=0.005). There was no correlation between IL-8 levels and ASUC treatment refractoriness (rs=0.22, p=0.3). Similarly, there was no difference in IL-8 levels in ASUC patients when classified by treatment response (Kruskal Wallis, p=0.5). Serum TNF level did not differ between healthy controls and patients with ASUC (19.5 and 22.2pg/mL, p=0.5). TNF levels did not correlate with treatment refractoriness in ASUC (rs=-0.06, p=0.75) and there were no differences between the ASUC response groups (p=0.6). Levels of GM-CSF, IFN-g, IL-2, IL-4 and IL-10 were predominantly below the detection limit of each assay. Conclusion In this ASUC cohort, serum IL-6 level on admission correlated with treatment refractoriness and may help identify patients at higher risk of requiring salvage therapy as well as those at higher risk of failing IFX. Further studies are needed to elucidate the function of IL-6 in ASUC and whether it may represent a potential predictor of outcomes in ASUC.