Is fecal calprotectin always normal in children with irritable bowel syndrome?

Background/Aims Fecal calprotectin (FC) is a marker of intraluminal intestinal inflammation. Intestinal inflammation may contribute to the pathophysiology of irritable bowel syndrome (IBS). This study evaluated FC levels in children with IBS and differences in FC levels in children stratified by IBS subtype and healthy controls (HCs). Methods A total of 157 children with IBS and 56 HCs aged 4–16 years (119 boys, 94 girls, mean age of 9.48 years) were included in this prospective study. Children with IBS were diagnosed using the Rome III criteria and classified into 4 subtypes: IBS with constipation (IBS-C, n=37), IBS with diarrhea (IBS-D, n=54), IBS with alternating constipation and diarrhea (IBS-M, n=49), and IBS unsubtyped (IBS-U, n=17); postinfectious IBS (PI-IBS) was also considered. The FC concentration in stool samples was analyzed using an enzyme-linked immunosorbent assay. All participants answered a questionnaire regarding several demographic and clinical characteristics. Results Children with IBS had significantly higher levels of FC than the HCs (88.71 μg/g vs. 17.77 μg/g). Among the 4 IBS subtypes, the FC concentration was highest in children with IBS-D, followed by those with IBS-M, IBS-C, and IBS-U (169.94 μg/g vs. 45.04, 31.22, and 33.52 μg/g, respectively), and these differences were statistically significant. For PI-IBS, 90% of cases were in the IBS-D group. Conclusions The FC level was significantly higher in children with IBS than in HCs and differed depending on the IBS subtype, supporting the notion that IBS is a type of low-grade bowel inflammation.