Plasma citrulline as surrogate marker of intestinal inflammation in pediatric and adolescent with Crohn's disease: preliminary report.

PURPOSE: Several researchers have found that plasma citrulline could be a marker of reduced enterocyte mass. The aim of this study was to assess the relationship between plasma citrulline and bowel inflammation and/or disease location in pediatric and adolescent Crohn's disease (CD) patients. METHODS: Between January 2008 and January 2010, 31 CD patients and 44 controls were included in our study, and 15 out of the 31 CD patients continued a prospective survey. We evaluated the differences between groups, at baseline, in plasma citrulline and glutamine and between their baseline and final values during the prospective survey, and correlation between baseline values of citrulline and duration of disease, C-reactive protein, and fecal calprotectin. RESULTS: Mean citrulline value was 33.0 ± 7.5 μmol/L in controls and 23.5 ± 8.4 μmol/L in CD patients (P < 0.0001). Plasma citrulline was significantly lower in patients with small bowel (SB) location than in patient with only ileo-colon disease (14.2 ± 5.5 and 24.7 ± 8.0, respectively; P = 0.0037). Citrulline ≤22 μmol/L reached sensitivity of 100% (95% confidence interval (CI) 54-100) and specificity of 98% (CI 89-99) in differentiating control subjects from CD with SB location. CONCLUSIONS: CD patients have reduced concentration of plasma citrulline than controls. Intestinal damage rather than inflammation seems to be responsible for the reduced biosynthesis of citrulline, which decreases particularly in CD patients with SB location. This finding suggests the potential role of citrulline as marker of disease location, but future works will be needed to confirm this suggestion.