S1300 The Relationship Between Serum IgA Level, Small Intestinal Bacterial Overgrowth (SIBO), and Ethnicity

Abstract

INTRODUCTION: Secretory immunoglobulin A (IgA) is critical in preventing pathogen overgrowth in the gastrointestinal tract. IgA production is stimulated by the colonization of bacteria. The relationship between serum IgA level & incidence of small intestinal bacterial overgrowth (SIBO) in symptomatic patients has not been studied. Patients with selective IgA deficiency with a critically low serum IgA level (< 7 mg/dL) & normal IgM & IgG levels have a 10- to 20-fold increased risk for celiac disease, however an increased risk for SIBO has not been documented. The aim of this retrospective observational study was to determine the relationship of abnormal serum IgA level as a possible risk factor for SIBO with stratification based on ethnicity. METHODS: A retrospective electronic chart review was performed of all patients seen in the gastroenterology clinic who underwent breath hydrogen testing for SIBO & had serum IgA level measurement from 12/1/2010 to 1/1/2020 via clinical data query. The relationship between serum IgA level, SIBO percentage in symptomatic patients via breath test results & patient demographics was studied. Continuous variables are presented by median & IQR. Categorical variables are presented by counts & percent. X2 test was used to test association between breath test results (abnormal/negative) & IgA levels (3 levels- reduced, normal & elevated). All statistical tests were performed at an α = 0.05 level of significance, using two-sided tests. RESULTS: 561 patients underwent breath hydrogen testing from 12/1/2010 to 1/1/2020 with documented serum IgA level, of which 73% were female, 53.7% Hispanic. 39.4% of breath tests were positive for SIBO; 3.7% were nondiagnostic. SIBO percentage was highest in patients with reduced IgA level (14/29, 48.3%) compared to normal (40.5%) or elevated IgA level (41.4%) (P = 0.7067). Reduced IgA level was more common in non-Hispanics than Hispanics (7.66 vs. 3.44%) whereas elevated IgA level was more common in Hispanics (7.22 vs. 3.40%). SIBO was more common in non-Hispanics with reduced IgA level than Hispanics (11/19, 57.9% vs. 3/12, 25%). CONCLUSION: The overall rate of SIBO is higher though not statistically significant in patients with reduced IgA. This may be due to an overall paucity of patients with abnormal IgA level in our population. Further, differences in ethnicity may impact IgA level & potential for SIBO. Future larger studies should explore the relationship of abnormal IgA level, SIBO & ethnicity.