Correlation between faecal excretion of indium-111-labelled granulocytes and calprotectin, a granulocyte marker protein, in patients with inflammatory bowel disease

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-1 11-labelled neutrophilic granulocytes has been suggested as the gold standa rd of disease activity, but its complexity and high cost and the exposure o f 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 (111) ln-labelled granulocytes. Methods: Calprotectin in stool extracts from 19 p atients with Crohn's disease (CD), 10 with ulcerative colitis (UC), and 9 p resumably healthy controls was assessed with a simple enzyme-linked immunos orbent assay. Simultaneously, the faecal excretion of autologous In-111-lab elled granulocytes was measured. Results: There was a strong correlation be tween the average daily excretion of calprotectin and that of the total 3-d ay excretion of In-111-labelled granulocytes (r = 0.87, P < 0.0001). Furthe rmore, the concentration of calprotectin, assessed in a small stool sample on day 1, also correlated well with the excretion In-111-labelled granulocy tes (r = 0.80, P < 0.0001). Conclusion: The results suggest that faecal cal protectin reflects the granulocyte migration through the gut wall in patien ts with IBD and hence might serve as a simple, inexpensive alternative to t he indium-111 technique.