Clinical Significance Of Serum Anti-mircobial Antibodies Test In Inflammatory Bowel Disease

ObjectiveInflammatory bowel disease (IBD) is characterized by chronic, recurrent inflammation of the gut and aberrant immunological response to commensal microbes in genetically susceptible individuals, with two major distinct clinical subtypes, Crohn’s disease (CD) and ulerative colitis (UC). Although the exact aetiology remains unknown,it is generally accepted that the pathogenesis of IBD may involve environmental, genetic, infectious and immunological factors. Current research indicate that inappropriate intestinal immune responses are drived by gut microbes in a susceptible host and result in chronic inflammation, which might play an important role in the IBD occurrence.This idea is supported by the occurrence of antibodies directed at several microbial antigens, such as ASCA, anti-OmpC, anti-I2and anti-CBirl. Furthermore, the presence of conventional serological markers could be used for disease stratification and they were associated with a more aggressive disease phenotype and a risk for surgery. The aim of this study is to assess the clinical unity of serum anti-Saccharomyces cerevisia antibody(ASCA),anti-outer membrane porin C(anti-OmpC), antibody to Pseudomonas fluorescens-associated sequence I2(anti-I2) and antibody to bacterial flagellin (anti-CBirl) in diagnosis and treatment of inflammatory bowel disease(IBD).MethodsFrom2011to2013,87patients with IBD from The First Affiliated Hospital of ZheJiang University School Of Medicine were enrolled and divided into Crohn’s disease(CD) group (66cases) and ulcerative colitis (UC) group (21cases). In CD patients, there are51males and15females with average36±15.1years; In UC patients, there are14males and7females with average46±14.5years, A total of62age and gender matched healthy individuals were enrolled as the control group.Fasting blood samples (2mL) of the subjects were collected. The expression of ASCA, anti-OmpC, anti-I2and anti-Cbirl antibodies was detected with enzyme-linked immunosorbent assay(ELISA) kits. The diagnosis value of each antibody in IBD and the differential diagnostic value of UC and CD were compared by receiver operating characteristic (ROC) curve.ResultsThe area under the curve (AUC) of ASCA between IBD and the healthy control group, between CD group and UC group was0.580and0.512,respectively; the accuracy in diagnosis was low. The AUC of anti-CBirl between IBD and the healthy control group was0.617.There was no differential diagnosis significance of the other antibodies.The positive rate of ASCA in IBD group was62.1%(54/87),which was significantly higher than that in the control group (38.7%,24/62). The positive rates of anti-OmpC and anti-I2in IBD group was significantly lower than those in the control group and the differences were statistically significant (both P<0.05).No difference was observed in positive rates of serum antibodies among the other groups(all P>0.05). The specificity, sensitivity, positive predictive value (PPV) and negative predictive value (NPV) of ASCA in differential diagnosis of CD and UC was52.4%,66.7%,81.48%and33.33%, respectively.The specificity and sensitivity of anti-OmpC. anti-I2and anti-CBirl in differential diagnosis of CD and UC was81%to100%and9.1%to37.9%,respectively.The specificity, sensitivity, PPV and NPV of double-positive ASCA and anti-I2in the diagnosis of CD was57.1%,86.4%,82.6%and50.0%,respectively. The positive rate of ASCA and anti-I2in CD group was significantly higher than that in UC group [84.8%(56/66) vs57.1%(12/21); X2=5.633, P=0.018].The expression levels of anti-OmpC and anti-CBirl in younger CD patients (age<40) were significantly higher than in elder patients (age>40). The expression level of the four antimicrobial antibodies had no correlation with disease activity (all P>0.05).ConclusionsPositive ASCA has some significance in the diagnosis of patients with IBD in our country. The detection of anti-I2can help to diagnose ASCA negative CD.To test antimicrobial antibodies in younger CD patients (age<40) may be more valuable. Because of low sensitivity and positive rate, anti-OmpC and anti-CBirl have limited value in the diagnosis of IBD and the differential diagnosis of UC and CD in our country. And those antibodies had no correlation with extent of disease activity.