Fecal calprotectin levels and serological responses to microbial antigens among children and adolescents with inflammatory bowel disease

Abstract

Background: Noninvasive, sensitive, and specific tools for early identification of chronic inflammatory bowel disease (IBD) are needed for clinical practice. The aim was to identify new noninvasive test combinations for characterization of IBD in children and adolescents by comparing serological responses to microbial antigens and fecal calprotectin, a new promising marker for intestinal inflammation.

Methods: Our study included 73 children who underwent endoscopies because of suspicion of IBD. Their sera were tested for antibodies to the Pseudomonas fluorescens-associated sequence I2, a Bacteroides caccae TonB-linked outer membrane protein, OmpW, and anti-Saccharomyces cerevisiae (ASCA). Simultaneously, samples for fecal calprotectin measurements were obtained from 55 subjects.

Results: IBD was diagnosed in 60 patients (Crohn's disease [CD] in 18 patients, ulcerative colitis [UC] in 36, and indeterminate colitis [IC] in 6). Thirteen children had a non-IBD disease. Fecal calprotectin levels were elevated (>or=100 microg/g) more frequently in IBD patients (89%, 39/44) compared to non-IBD cases (9%, 1/11, P < 0.001). ASCA antibodies in sera were detected in 67% (12/18) of patients with CD, in 14% (5/36) of the children with UC, and in 50% (3/6) of patients with IC. Seroreactivity for I2 was observed in 42% of the IBD patients, this frequency being higher than in non-IBD cases (7.7% seropositive; P = 0.025). Serum anti-I2 IgA levels (median absorbances) were higher in those with IBD compared to those without gut inflammation (P = 0.039). The combination of the measurements of fecal calprotectin and serological responses to microbial antigens (ASCA, I2, and OmpW) identified 100% of CD patients (sensitivity 100%, specificity 36%, positive predictive value [PPV] 66%, negative predictive value [NPV] 100%) and 89% of UC patients (sensitivity 89%, specificity 36%, PPV 77%, NPV 57%).

Conclusions: Increased levels of serological responses to microbial antigens (ASCA, I2, and OmpW) and fecal calprotectin are evident in both CD and UC patients. The combination of these markers provides valuable, noninvasive tools for the diagnosis of IBD.

FIGURE 1

Fecal calprotectin levels in children and adolescents according to diagnosis into inflammatory bowel disease (IBD) subgroups (Crohn’s disease; CD, ulcerative colitis; UC and indeterminate colitis; IC) and non-IBD group. Horizontal line denotes the cut-off value for positivity (see text). P values compare absorbances between the IBD subgroups and non-IBD group, using the Mann-Whitney U-test.

FIGURE 2

Serological responses to the Pseudomonas fluorescens-associated sequence I2 (A) and Bacteroides caccae TonB-linked outer membrane protein OmpW (B) in children and adolescents according to their diagnosis into inflammatory bowel disease (IBD) and non-IBD group. Horizontal lines denote the cut-off values for seropositivity (see text). P values compare absorbances between the IBD and non-IBD groups, using the Mann-Whitney U-test.

FIGURE 2

Serological responses to the Pseudomonas fluorescens-associated sequence I2 (A) and Bacteroides caccae TonB-linked outer membrane protein OmpW (B) in children and adolescents according to their diagnosis into inflammatory bowel disease (IBD) and non-IBD group. Horizontal lines denote the cut-off values for seropositivity (see text). P values compare absorbances between the IBD and non-IBD groups, using the Mann-Whitney U-test.

FIGURE 3

Serological responses to the Pseudomonas fluorescens-associated sequence I2 in 51 children and adolescents with inflammatory bowel disease (IBD) at the time of diagnosis. Patients are grouped according to their final diagnosis into Crohn’s disease (CD), ulcerative colitis (UC), indeterminate colitis (IC) and non-IBD patients. Horizontal lines denote the cut-off value for seropositivity (see text). P values compare absorbances between the IBD and non-IBD groups, using the Mann-Whitney U-test.

FIGURE 4

Relationship between serum antibodies to Saccharomyces cerevisiae, the Pseudomonas fluorescens-associated sequence I2 and to a Bacteroides caccae TonB-linked outer membrane protein, OmpW and 51 inflammatory bowel disease (IBD) patients at the time of primary diagnosis by presence vs. absence. The percentage of patients positive for any of each marker and of two or all three markers is presented.