P404 Monocyte distribution width differentiates bacterial gastroenteritis from Acute Severe Ulcerative Colitis in patients presenting with diarrhoea

Abstract

Abstract Background Monocyte distribution width (MDW) is a haematological parameter that can be generated by newer generation blood analysers on routine full blood examination. It reflects the variation in the size of monocytes and is elevated in the setting of infection, however its utility in inflammatory disorders in unknown. We aimed to assess whether MDW can help differentiate bacterial gastroenteritis from Acute Severe Ulcerative Colitis (ASUC) among patients presenting to the Emergency Department (ED) with diarrhoea. We further aimed to assess whether MDW correlated with disease activity and clinical outcomes in ASUC. Methods We conducted a retrospective cohort study comprising three patient groups: (1) ASUC, (2) bacterial gastroenteritis and (3) a control group of patients without active inflammation. The control group consisted of outpatients with chronic hepatitis B in immune control phase with normal liver transaminases and suppressed viral load < 2000 IU/mL. Clinical outcomes, routine biomarkers and MDW were recorded. Results A total of 176 patients were identified (53 ASUC, 70 bacterial gastroenteritis and 53 controls). At time of ED presentation, patients with bacterial gastroenteritis had the highest MDW (median 23.6, IQR 20.7-25.8) compared to ASUC (19.0, IQR 17.9-21.2) and controls (16.8, IQR 15.9-18.0; P<0.001). On receiver operator characteristic curve analysis, MDW discriminated bacterial gastroenteritis from ASUC with an area under the curve (AUC) of 0.78 (95% CI 0.70-0.87, P<0.001). Using Youden’s index, a MDW threshold > 22.3 had 64.3% sensitivity, 84.6% specificity, 63.8% negative predictive value and 84.9% positive predictive value for bacterial gastroenteritis. Of the 53 patients with ASUC, 25 responded to intravenous hydrocortisone while 28 were steroid non-responders and required infliximab (IFX). 24 patients responded to IFX rescue, while the 4 IFX non-responders received tofacitinib sequential therapy. In ASUC, MDW correlated positively with established markers of disease activity including CRP (Spearman rank correlation, rho=0.54, P<0.001), platelet count (rho=0.36, P=0.009) and faecal calprotectin (rho=0.35, P=0.02). A lower MDW on the day of IFX administration appeared to predict IFX response (AUC 0.80, 95% CI 0.61-1.00, P=0.002). At follow-up (median 85 days), MDW was predictive of biochemical remission with a faecal calprotectin < 100 µg/g (AUC 0.80, 95% CI 0.64-0.95, P<0.001). Conclusion MDW is a novel biomarker that may help distinguish ASUC from bacterial gastroenteritis at time of ED presentation in patients with diarrhoea. In ASUC, MDW correlates with existing markers of activity and may help predict IFX response.