Are activity indices helpful in assessing active intestinal inflammation in Crohn's disease?

We have investigated the correlation of 24 h and 48 h faecal Indium-111 excretion with each other and with several clinical activity indices for Crohn's disease (CD): Crohn's disease activity index (CDAI), activity index (AI), simple index (SI), Oxford score, and laboratory parameters, such as ESR, serum albumin, orosomucoid, C-reactive protein, alpha-l-antitrypsin (alpha 1-AT) faecal concentration, and alpha 1-AT clearance in 58 CD patients (37 with small bowel and 21 with colonic disease). A significant correlation was found between 24 and 48 h faecal Indium-111 excretion for small bowel (r = 0.708, p less than 0.0001) and colonic disease (r = 0.994, p less than 0.0001). The median faecal Indium-111 excretion for colonic involvement (4%; 0.15-50% median and range) was significantly (p less than 0.005) higher than that for small bowel disease (0.45%; 0.03-2.9%). No significant correlation was found between faecal Indium-111 excretion and any activity index in the patients with small bowel disease, while in the group of patients with colonic localisation only the AI showed a significant correlation (r = 0.593, p less than 0.02). Faecal Indium-111 excretion was significantly correlated with alpha 1-AT clearance (r = 0.712, p less than 0.0001) and faecal alpha 1-AT concentration (r = 0.750, p less than 0.0001) in small bowel and in colonic localisation (r = 0.530, p less than 0.02 and r = 0.444, p less than 0.05). Serum albumin was significantly correlated only in the group of patients with colonic disease (r = -0.593, p less than 0.05). The present study shows poor agreement between activity indices, serum parameters of activity and faecal Indium-111 excretion. As a good correlation was found with the alpha1-clearance, which reflects losses into the gut, these results may suggest that faecal Indium excretion does not only reflect activity of inflammation, but my relate to the extent of intestinal ulceration.