Usefulness of peripheral blood monocyte count to predict relapse in patients with inflammatory bowel disease: a prospective longitudinal cohort study.

Background: monocytes play an important role in the pathogenesis of inflammatory bowel disease but data are scarce regarding activity biomarkers, above all in patients under biologic therapies.
Objective: the aim of this study was to evaluate the value of monocyte measurements in predicting flares in inflammatory bowel disease patients under maintenance treatment with anti-TNF.
Methods: a prospective, observational cohort study was designed. Relapse was defined as a Harvey-Bradshaw score > 4 in Crohn's disease, and a partial Mayo score ≥ 2 in ulcerative colitis. Monocyte concentration was quantified at 4-month intervals for twelve months. A total of 95 consecutive patients were included. Median age was 42 years, 50.5 % were female, and 75 % had Crohn's disease.
Results: sixteen months after inclusion, 65 (68.4 %) patients remained in clinical remission. Mean monocyte count preceding a relapse was 563 (standard deviation: 144) compared to 405 (standard deviation: 177) in patients who remained in remission. Final monocyte count was significantly different between relapse and remission in Crohn's disease (0.82; 95 % CI: 0.71-0.90; p < 0.005). According to the multivariate analysis, only monocytes and fecal calprotectin were related to more relapses.
Conclusion: in conclusion, in inflammatory bowel disease patients under anti-TNF therapy, repeat monocyte counts could help monitor patients, at least in Crohn's disease.