Fecal calprotectin: validation as a noninvasive measure of bowel inflammation in childhood inflammatory bowel disease

Background: Calprotectin is an abundant neutrophil protein, which is extremely stable in feces. This study aimed to validate fecal calprotectin as a marker of bowel inflammation against invasive measures in children with inflammatory bowel disease (IBD), including colitis and small bowel Crohn disease.

Methods: Fecal calprotectin was measured using a simple enzyme-linked immunosorbent assay in 36 spot stool samples from 22 children before colonoscopy and from 14 children before technetium-99 (Tc-99) scanning. Using standard scoring systems, the severity of inflammation was assessed macroscopically and histologically at six standard sites in those who underwent colonoscopy and also at six standard sites in those who underwent Tc-99 scanning. The subscores from each site were summated to give combined severity and extent scores for macroscopic and for histologic inflammation in the group undergoing colonoscopy and total inflammation in the group undergoing 99Tc scanning.

Results: In the 22 children who underwent colonoscopy, median fecal calprotectin was 4.9 mg/L (0.1-272.5 mg/L) (range). Disease groups included six normal cases, nine ulcerative colitis cases, two isolated Crohn colitis cases, two indeterminate colitis cases, and three allergic colitis cases. Fecal calprotectin correlated closely with colonic macroscopic inflammation (r = 0.75, P < 0.001) and histologic inflammation (r = 0.85, P < 0.001). Of the 14 children undergoing Tc-99 scanning, 10 had Crohn disease, 3 had ulcerative colitis, and I had allergic colitis. Median fecal calprotectin was 9.1 mg/L (0.3-141.7 mg/L), and this correlated closely with the Tc-99 scanning score (r 0.80, P = 0.001).

Conclusion: Fecal calprotectin correlates closely with the best invasive measures of colonic and small bowel inflammation in childhood inflammatory bowel disease. As a sensitive objective measure of bowel inflammation that is risk-free and noninvasive, fecal calprotectin lends itself particularly to the monitoring of and assessment or therapeutic interventions in children with inflammatory bowel disease.