Recent studies have identified the role of serological markers in characterizing disease phenotype, location, complications and severity among Caucasians with Crohn's Disease (CD). However, very little is known about the role of serology in CD in African Americans (AA). The primary aim of this study is to evaluate common IBD antimicrobial serologic antibodies in AA with CD to determine their association with disease phenotype, location and severity, while controlling for genetic ancestry.Methods:
AAs with CD were enrolled as participants through multi-center collaborative efforts. Serological levels of IgA ASCA, IgG ASCA, anti-OmpC, anti-CBir, and ANCA were measured using enzyme linked immunosorbent assays. Genotyping was performed using Illumina immunochip technology and admixture rate was calculated for each subject. 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:
Three hundred fifty-eight patients were included in the analysis. The majority of our patients had inflammatory, non-complicated disease (58.4%), perianal disease (55.7%), and documented colonic inflammation (86.8%). On multivariable analysis, IgG ASCA was associated with complicated disease (OR: 3.2; 95% confidence interval (CI), 0.79–5.88) and surgery (OR: 3.3; 95% CI, 0.72–5.69), while anti-OmpC was associated with surgery only (OR: 2.33; 95% CI, 0.28–4.25). Caucasian admixture to African genome did not have any associations or interactions in relation to clinical outcome.Conclusions:
The diagnostic value of serological antibodies appears comparable in AA to Caucasians with CD with respect to IgG ASCA and anti-OmpC suggesting that perhaps these similarities are more of a function of likenesses among the intestinal microbiome than differences in genetic make-up, further emphasizing the role of the environment and the limitation of genetics to predict or diagnose IBD.