P015 Familial prevalence of serologic markers of IBD in a Hispanic cohort

P015 Familial prevalence of serologic markers of IBD in a Hispanic cohort 

Michelen-Gómez Eduardo1, Llorens-Bonilla Aidaliz1, Ruiz-Serrano Krystel1, McGovern Dermot2, Targan Stephan2, Torres Esther1
1 University of Puerto Rico, Medical Sciences Campus, San Juan, United States, 2 Inflammatory Bowel Disease Center, Cedars Sinai Medical Center, CA, Los Angeles, United States

BACKGROUND: To describe the prevalence of serologic markers in Hispanics with Inflammatory Bowel Disease (IBD) and their unaffected parents. Serum markers evaluated were ANCA, ASCA IgA, ASCA IgG, CBir1, I2, and OmpC. We determined the association of specific markers with diagnoses: Crohn’s disease (CD) versus ulcerative colitis (UC); examined the presence and levels of serum markers in the unaffected parents (familial controls) and compared them with the subjects with IBD (cases). 

METHODS: Subjects were Hispanic participants in the NIDDK IBD Genetics Research Consortium. We selected a familial cohort of trios (subject plus unaffected parents) and tetrads (2 affected siblings plus unaffected parents). IBD diagnosis was established by standard criteria. Serologic markers were performed using ELISA and reported in EU/ml. The results were classified as positive or negative according to the mean levels of each group. Cutoff values for positive serologies in EU/ml were: ANCA=35, CBir1=30, I2=30, ASCA IgA=20, ASCA IgG=40 and OmpC=23. Descriptive statistics was used to summarize continuous variables using mean and standard deviation. Categorical variables were described using frequencies and percentages. The protocol is approved by the MSC-IRB.

RESULTS: Of the 286 subjects in the cohort, 98 were cases and 188 were controls. There were 90 trios and 4 tetrads.  64 subjects had CD and 33 had UC. The mean values of individual markers for each study group were assessed. Subjects with UC were positive for ANCA (mean level of 41.79). Subjects with CD were positive for CBir1 (mean=40.30), I2 (mean=44.83), ASCA IgG (mean=43.94) and OmpC (mean=23.08). The mean values for the parents of both groups were in the negative range. However, within each diagnostic group, several parents had positive antibody titers. Particularly, 18.3% and 21.9% of UC and CD parents, respectively, were positive for I2 and 11.3% and 13% of UC and CD parents, respectively, were positive for OmpC. 
 
CONCLUSION(S): This study suggests that serologic markers in Hispanics with IBD follow the same pattern as that of other ethnic groups. However, the prevalence of positive pANCA is similar for UC and CD, and lower for UC and higher for CD than reported in other groups. Likewise, the prevalence of OmpC in subjects with CD was lower than expected (40.6 vs 55%), as was I2 (40.6% vs 55%). ASCA has also been reported to be present in 20 to 25% of first-degree relatives of patients with CD, whereas our group showed only 13.3%. These discrepancies deserve further study. They may represent genetic differences between populations, but this has not been shown to date in genetic studies. Variation in environmental exposures based in the geographic location of the population is an attractive consideration and may explain the presence of diverse antibodies in parents of both UC and CD subjects.