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P745 Incidence of indeterminate colitis in the EPIMAD registry decreases over the period 1988–2014

P. Mayer*1, H. Sarter2,3, M. Fumery2,4, G. Savoye5, A. Leroyer3, L. Dauchet3, C. Gower-Rousseau2,3, B. Pariente1

1Lille University Hospital, Gastroenterology Unit, Hôpital Huriez, Lille, France, 2Lille University, CHRU de Lille, Lille Inflammation Research International Centre LIRIC - UMR 995 Inserm, Lille, France, 3Lille University and Hospital, Public Health, Epidemiology and Economic Health, Register Epimad, Lille, France, 4CHU Amiens Sud, l, Amiens University Hospital, Gastroenterology Unit, Epimad Registry, Amiens, France, 5Hôpital Charles Nicolle, Rouen University Hospital, Gastroenterology Unit, Epimad Registry, Rouen, France

Background

Inflammatory bowel disease unclassified (IBDU) represents 5–15% of new diagnosis of inflammatory bowel disease. However, IBDU is not well defined and high rate of reclassification in Crohn’s disease (CD) or Ulcerative colitis (UC) is observed during follow-up. The objective of the present study was to evaluate the evolution of the incidence of IBDU over the period 1988–2014 in a population-based study and its reclassification rate during the follow-up.

Methods

All adults (> 17 years old) patients diagnosed with IBDU according to a validated and published algorithm1 in the French population-based registry EPIMAD from 1988 to 2014, were identified. Follow-up was divided in 3 periods of 9 years (1988–1996, 1997–2005, and 2006–2014). Reclassification was defined as a modification of diagnosis during the follow-up.

Results

24 304 IBD cases (> 17 years) were diagnosed, including 8449 (66.2%) CD, 3839 (30.1%) UC and 476 (3.7%) IBDU. IBDU concerned predominantly males compared with CD and UC population [(51.7% in IBDU population (n = 246) vs. 45.6% in CD plus UC population (n = 5602) (p = 0.009)], with an older age at diagnosis [(36 [26–51] in IBDU population vs. 30 [28–42] in CD plus UC population (p < 0.001)]. IBDU rate among IBD diagnosis decreased significantly during the study period, from 6% (1988–1996) to 2% (2006–2014) (p < 0.0001). In the IBDU cohort, 334 (70.2%) only had one diagnosis; 132 (27.7%) had two and 10 (2.1%) had three during follow-up. IBDU reclassification occurred in 108 patients (22.7%). The median time for reclassification was 1 year (IQR [1 −2]) after the diagnosis. Eighty-nine patients (18.7%) were reclassified to CD or UC after a new flare. There was no significant modification of IBDU reclassification rate in CD or UC during the study period 17% (1988–1996) to 21% (2005–2014) (p = 0.56).

Conclusion

In this population-based study, IBDU incidence decreased significantly between 1988 and 2014, probably because of better diagnosis performances allowing CD and UC identification. These results suggest that IBDU may not be a real and significant clinical entity but a misclassification of colonic inflammatory bowel disease.

Reference

1. Gower-Rousseau et al. Incidence of inflammatory bowel disease in northern France (1988–1990). Gut 1994.