Su2034 Diagnosis of Small Intestinal Bacterial Overgrowth by Lactulose Hydrogen Breath Test With Scintigraphic Oro-Caecal Transit Test: Methodological Validation of Diagnostic Criteria in Healthy Controls and Patients With Diarrhea Predominant Irritable Bowel Syndrome

Abstract

INTRODUCTION: The prevalence of small intestinal bacterial overgrowth (SIBO) in irritable bowel syndrome (IBS) patients remains contentious due to continuing uncertainty regarding diagnostic methodology. The lactulose hydrogen breath test (LHBT) is used to detect SIBO; however, recent papers have suggested that the results are confounded by wide variation of oro-caecal transit time. Combination with an independent, scintigraphic assessment of oro-cecal transit time (SOCTT) may address this problem with SIBO diagnosed when there is a rise in breath hydrogen before scintigraphic marker is seen in the caecum. AIM: To determine the most appropriate diagnostic criteria and clinical relevance of SIBO diagnosed using LHBT alone and combined HBT/SOCTT. SUBJECTS: 60 patients with diarrhea predominant irritable bowel syndrome (D-IBS) and 13 healthy controls. METHODS: A systematic analysis of the ability of six published diagnostic criteria to detect SIBO in D-IBS patients and controls was performed (Criteria 1: A H2 rise of ≥20ppm within 180 min; Criteria 2: A H2 rise of ≥20ppm within 90 min; Criteria 3: dual breath H2 peaks; Initial H2 rise, ≥5ppm (Criteria 4), 10ppm (Criteria 5) and 20ppm (Criteria 6) above baseline before the scintigraphic OCTT). In a subgroup of these patients the clinical relevance of these diagnostic markers was tested in an open label study of antibiotic therapy (rifaximin 1200mg/d, 10days). The short-term effect of this treatment on D-IBS symptoms in patients with and without SIBO was assessed. RESULTS: There was a close association between the time to breath H2 increase to 5ppm and 20ppm on LHBT and scintigraphic OCTT in health (R5ppm =0.896, p,0.001; R20ppm =0.860, p=0.003); however this association was lost in D-IBS patients (R5ppm =0.214, p=0.165). A 5ppmH2 increase prior to appearance of cecal contrast (criteria 4) was detected in more D-IBS patients than healthy subjects (28/60 vs. 1/13; p=0.009). This was not the case for other candidate diagnostic markers. Compared to D-IBS patients with negative findings (n=9/32), patients with a positive diagnosis of SIBO based on criteria 4 (n=27/28) had improved D-IBS symptoms following antibiotic therapy (table 1). CONCLUSIONS: Combined LHBT/scintigraphy is required for non-invasive SIBO diagnosis. The presence of a 5ppm increase in breath H2 prior to the arrival of contrast in the cecum may identify a subset of D-IBS patients with SIBO that have good clinical outcomes following antibiotic therapy.