Development and validation of a biomarker for diarrhea-predominant irritable bowel syndrome in human subjects

Abstract

Diarrhea-predominant irritable bowel syndrome (IBS) is diagnosed through clinical criteria after excluding "organic" conditions, and can be precipitated by acute gastroenteritis. Cytolethal distending toxin B (CdtB) is produced by bacteria that cause acute gastroenteritis, and a post-infectious animal model demonstrates that host antibodies to CdtB cross-react with vinculin in the host gut, producing an IBS-like phenotype. Therefore, we assessed circulating anti-CdtB and anti-vinculin antibodies as biomarkers for D-IBS in human subjects. Subjects with D-IBS based on Rome criteria (n=2375) were recruited from a large-scale multicenter clinical trial for D-IBS (TARGET 3). Subjects with inflammatory bowel disease (IBD) (n=142), subjects with celiac disease (n=121), and healthy controls (n=43) were obtained for comparison. Subjects with IBD and celiac disease were recruited based on the presence of intestinal complaints and histologic confirmation of chronic inflammatory changes in the colon or small intestine. Subjects with celiac disease were also required to have an elevated tTG and biopsy. All subjects were aged between 18 and 65 years. Plasma levels of anti-CdtB and anti-vinculin antibodies were determined by ELISA, and compared between groups. Anti-CdtB titers were significantly higher in D-IBS subjects compared to IBD, healthy controls and celiac disease (P<0.001). Anti-vinculin titers were also significantly higher in IBS (P<0.001) compared to the other groups. The area-under-the-receiver operating curves (AUCs) were 0.81 and 0.62 for diagnosis of D-IBS against IBD for anti-CdtB and anti-vinculin, respectively. Both tests were less specific in differentiating IBS from celiac disease. Optimization demonstrated that for anti-CdtB (optical density≥2.80) the specificity, sensitivity and likelihood ratio were 91.6%, 43.7 and 5.2, respectively, and for anti-vinculin (OD≥1.68) were 83.8%, 32.6 and 2.0, respectively. These results confirm that anti-CdtB and anti-vinculin antibodies are elevated in D-IBS compared to non-IBS subjects. These biomarkers may be especially helpful in distinguishing D-IBS from IBD in the workup of chronic diarrhea.

Conflict of interest statement

Competing Interests: The authors have read the journal's policy and the authors of this manuscript have the following competing interests: Cedars-Sinai has a licensing agreement with Salix Pharmaceuticals, Commonwealth Laboratories, and Synthetic Biologics, Inc. Dr. Mark Pimentel is a paid consultant for Salix Pharmaceuticals, Commonwealth Laboratories, Micropharma Inc. Naia Pharmaceuticals and Synthetic Biologics Inc. Dr. Mark Pimentel and Dr. Christopher Chang are on the advisory board for Salix Pharmaceuticals. Dr. Anthony Lembo is a consultant for Salix Pharmaceuticals and Ironwood Pharmaceuticals. The remaining authors have no competing interests to disclose. The authors thank the Cedars-Sinai Inflammatory Bowel Disease Program for providing the blood samples from patients with inflammatory bowel disease used in this study. This does not alter the authors' adherence to PLOS ONE policies on sharing data and materials.

Figures

Fig 1. Comparison of optical density (OD) for the anti-CdtB antibody among the groups.

Titers were higher in IBS subjects when compared to any other group (P<0.001). Titers were also higher in subjects with celiac disease when compared to healthy controls and IBD subjects (P<0.001). Dots represent outlier subjects beyond the whisker plot.

Fig 2. Comparison of optical density (OD) for the anti-vinculin antibody among the groups.

Titers were higher in IBS subjects when compared to any other group (P<0.001). Dots represent outlier subjects beyond the whisker plot.

Fig 3. Receiver operator curve (ROC) comparing anti-CdtB and anti-vinculin levels in D-IBS subjects and IBD subjects.

CI, confidence interval.