Correlation between Faecal Excretion of Indium-111-Labelled Granulocytes and Calprotectin, a Granulocyte Marker Protein, in Patients with Inflammatory Bowel Disease

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Abstract
Background: Several studies have suggested that clinical indices of disease activity in inflammatory bowel disease (IBD) do not adequately reflect the degree of inflammation in most such patients. Faecal excretion of indium-111-labelled neutrophilic granulocytes has been suggested as the gold standard of disease activity, but its complexity and high cost and the exposure of patients to ionizing irradiation have limited the use of this technique. The aim of this study was to investigate the correlation between the faecal excretion of the granulocyte marker protein calprotectin and that of 111In-labelled granulocytes. Methods: Calprotectin in stool extracts from 19 patients with Crohn's disease (CD), 10 with ulcerative colitis (UC), and 9 presumably healthy controls was assessed with a simple enzyme-linked immunosorbent assay. Simultaneously, the faecal excretion of autologous 111In-labelled granulocytes was measured. Results: There was a strong correlation between the average daily excretion of calprotectin and that of the total 3-day excretion of 111In-labelled granulocytes (r = 0.87, P < 0.0001). Furthermore, the concentration of calprotectin, assessed in a small stool sample on day 1, also correlated well with the excretion 111In-labelled granulocytes (r = 0.80, P < 0.0001). Conclusion: The results suggest that faecal calprotectin reflects the granulocyte migration through the gut wall in patients with IBD and hence might serve as a simple, inexpensive alternative to the indium-111 technique.