P225 Usefulness of monocytosis as biomarker to predict relapse in inflammatory bowel disease patients in remission under maintenance treatment with anti-TNF drugs: A prospective longitudinal cohort study

Abstract

Background: Monocytes play an important role in the pathogenesis of inflammatory bowel disease and recently have been shown to be a biomarker of activity, but there are no specific data in severe patients under anti-TNF therapies. The aim of the study was to determine the value of monocyte measurements in predicting flares in IBD patients in remission under maintenance treatment with anti-TNF drugs. Method(s): A prospective, observational cohort study was designed. Inclusion criteria were IBD patients in clinical remission for at least six months under a continuous standard dose of 40 mg/eow adalimumab therapy or 5mg/kg infliximab therapy every 8 weeks. Relapse was defined as a Harvey-Bradshaw score >4 in Crohn's disease (CD) and a partial Mayo score>3 in ulcerative colitis (UC). Monocytosis was defined as a monocyte count above 800 and they were quantified at 4-month intervals for 12 months. Other biomarkers like fecal calprotectine (FC), C reactive protein (CRP) and erythrocyte sedimentation rate (ESR) were obtained and evaluated at the same time as monocyte count. All patients completed a basal demographic and clinical questionnaire. Diagnostic accuracy of monocytosis for predicting relapse was evaluated by ROC curve analysis. Result(s): 95 patients with more than six months in remission under anti-TNF treatment were consecutively included. The median age was 44 years, 51% female and 75% with CD. Sixty-five (68.4%) patients remained in clinical remission and 30 (31.6%) suffered from a relapse during the follow-up period. Median monocyte concentration in the sample preceding the relapse was 500 (range 300-1000) compared with 400 (range 0-700) at the end of follow-up in patients who remained in remission. In the multivariate analysis The presence of monocytosis was related to more relapses [OR 7.13 (95% CI 1.54-32.8)]. Nevertheless, diagnostic accuracy of monocytosis was not very reliable (AUC 0.59, 95% CI 0.49-0.69) because it has excellent specificity (95.4%) but very low sensitivity (23.3%). Compared with other biomarkers accuracy was higher only with FC (AUC 0.93 95% CI 0.89-0.98). Conclusion(s): In IBD patients under anti-TNF therapy, repeated monocytosis could help in order to predict relapses. The accuracy of monocytosis is lower than FC. The use of monocyte counts in clinical practice is still controversial due to their low sensitivity.