Can concurrent lower gastrointestinal manifestations help the timely diagnosis of small intestinal bacterial overgrowth in CVID patients?

Gastrointestinal complications are considered as one of the most common manifestations in patients with Common Variable Immunodeficiency (CVID). These complications can result from Small Intestinal Bacterial Overgrowth (SIBO). Hydrogen breath test is extensively used to diagnose SIBO. The objective of this study was to evaluate the prevalence of SIBO using the Hydrogen Breath Test (HBT) in patients with CVID. Twenty-seven patients with CVID entered this cross-sectional study. Demographic and lower gastrointestinal symptoms were recorded in a check list. Hemoglobin level was measured in all patients. The concentration of IgA and IgG was assessed using nephelometry. Moreover, SIBO was detected by means of Glucose hydrogen breath test. The mean (plus-minus SD) age of the patients was 35.25 (plus-minus 11.69) years. Twenty patients (74.1%) manifested at least one lower gastrointestinal symptom. The most frequent lower gastrointestinal manifestations were bloating (66.7%) and chronic diarrhea (40.7%), respectively. IgA level less than 10 mg/dl and IgG level less than 600 mg/dl were determined in 77.8% and 25.9% of patients, respectively. Positive HBT was detected in 40.7% (n = 11) of the patients. In the positive HBT group, bloating, chronic diarrhea and abdominal pain were the most common lower GI manifestations. There was no significant difference in terms of age, BMI, IgA level, and duration of CVID between the positive and negative HBT groups. The significant association of co-occurrence of anemia and abdominal pain with positive HBT (positive predictive value: 100%) might be considered as a clue to SIBO diagnosis. Regarding the high prevalence and non-specific manifestation of SIBO, it is suggested to consider concurrent symptoms in patients with CVID to manage the timely and precise diagnosis of SIBO.