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P551. Association between haemoglobin levels, serum ferritin and faecal and serum markers of inflammation in patients with IBD

N.S. Taylor, S. Cotton, L.-A. McCabe, D.A. Lloyd, J.N. Gordon, Royal Hampshire County Hospital, Hampshire Hospitals NHS Foundation Trust, Department of Gastroenterology, Winchester, United Kingdom

Background

Anaemia is common in IBD and usually due to either iron-deficiency or anaemia of chronic disease. Serum ferritin is a frequently used marker of iron status in patients with IBD. It is influenced by inflammatory status with CRP commonly used in clinical practice to aid in determining the presence or absence of iron deficiency. However, the correlation of ferritin with markers of mucosal disease activity such as faecal calprotectin (FC) has not been studied and has important implications in determining the effect of inflammation on the diagnosis of iron deficiency. The aim of this study was to investigate the relationship between haemoglobin, serum ferritin and faecal and serum markers of inflammation in IBD.

Methods

We performed a computer database search of all IBD clinic patients who had paired blood tests (including Hb, mean cell volume, CRP, ferritin) and FC in the last 12 months. Blood and faecal samples were accepted as paired if taken within 7 days of each other. Anaemia was defined using WHO criteria, with a ferritin of <30 ng/ml taken to indicate iron-deficiency. An FC of <50 ug/g was taken to indicate inactive disease, an FC of 50–200 ug/g a borderline result and an FC >200 ug/g as active disease. Results were analysed to assess for prevalence of anaemia and iron deficiency and their correlation with faecal and biochemical markers of disease activity.

Results

124 patients (79 Crohn's disease, 45 ulcerative colitis) with a diagnosis of IBD and paired blood tests and faecal inflammatory markers were identified and their data analysed. 21% of the whole cohort were anaemic, and 34% were iron-deficient. There was a clear negative correlation between disease activity and both haemoglobin and ferritin levels. 9% of patients with an FC <50 ug/g, 17% with FC 50–200 ug/g and 36% with FC >200 ug/g were anaemic (p < 0.001). 24% with an FC <50 ug/g, 27% with an FC of 50–200 ug/g and 50% with FC >200 ug/g were iron deficient (p < 0.001). 65% of patients with an FC >200 ug/g had a normal CRP (<5 mg/l). Nearly double the number of anaemic patients would have been classified as having active disease by raised Calprotectin (65% FC >200 ug/g) compared with CRP (35% CRP >5 mg/l).

Conclusion

Anaemia (21%) and iron deficiency (34%) were common in this cohort of patients with IBD. There was a clear negative correlation between markers of anaemia and iron deficiency and faecal calprotectin. A raised FC of >200 ug/g should be a prompt to check iron stores, as iron-deficiency is extremely common in this group (50%). In this study the use of FC in preference to CRP to identify patients with active disease IBD would result in almost twice as many patients with anaemia being classified as having iron deficiency.