The Characterization of Antimicrobial and Autoimmune Antibodies in African-Americans with Crohn's Disease Open Access

Bertha, Madeline McGuire (2015)

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Background: Crohn's disease (CD) is a chronic, relapsing and remitting, inflammatory disease that affects the small bowel and/or colon. Recent studies have identified the role of antimicrobial and autoimmune antibodies in characterizing disease phenotype, location, complications and severity among Caucasians with CD. Despite these advances, very little is known about the nature of CD among African Americans (AA). This study will explore the relationship between serological antibodies and disease phenotype in AAs with CD and assess for their interaction with % African ancestry.

Methods: AAs with CD were enrolled as participants of 2 large IBD databases (GENESIS and BIG). Data on clinical features were obtained by patient interview or retrospective chart review. Serological levels of IgA ASCA, IgG ASCA, anti-OmpC, anti-CBir1, and pANCA were measured using enzyme linked immunosorbent assays. Genotyping was performed using Illumina immunochip technology. Multiple imputation by chained equations was performed to account for data missing at random. Logistic regression was used to calculate adjusted odds ratios (OR) for associations between serological markers and complicated disease, ileal disease, and disease requiring surgery.

Results: 358 patients were included in the analysis. The majority of our patients had inflammatory, non-complicated type disease (58.4%), perianal disease (55.7%), and disease involving the colon (86.8%). On multivariable analysis, IgG ASCA (comparing the 75%ile to the 25%ile) was associated with complicated disease (OR: 3.21; 95% confidence interval (CI) 1.98, 5.21), ileal disease (OR: 2.42; 95% CI: 1.30, 9.02), and surgery (OR: 3.13; 95% CI: 1.72 , 5.69). IgA ASCA was associated with ileal disease (OR: 3.42; 95% CI: 1.30 , 9.02). pANCA was associated with ileal disease (OR: 0.81; 95% CI: 0.68, 0.97). Anti-OmpC was associated with surgery (OR:2.33; 95% CI 1.28, 4.25).

Conclusions: Anti-OmpC is an independent risk factor for surgery in AA. There is no interaction between % African ancestry and serological levels, however we had inadequate power to investigate this hypothesis. The diagnostic value of serological antibodies may vary significantly among different ethnicities and, therefore, should be interpreted differently in AA compared with Caucasians.

Table of Contents

List of Tables and Figures. i

Appendix. ii

Introduction. 1

Background. 2

Methods. 5

Results. 12

Discussion. 16

References. 20

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