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“The findings of the lactulose breath test in Irritable Bowel Syndrome patients have been used to suggest that most patients have small intestinal bacterial overgrowth (SIBO), and this association has spawned the widespread use of antibiotics in IBS. The study by Bratten and colleagues demonstrates that this test does not discriminate between IBS patients and healthy controls when criteria from recent clinical IBS studies are applied. When the findings from this large study are combined with previous smaller studies, they challenge the hypothesis that SIBO underlies the symptoms of IBS and undermine the current rationale for the use of antibiotics in IBS.” Source: American Journal of Gastroenterology, Apr 2008, pp. 964-65]

Introduction: Recent reports suggest that abnormalities of lactulose breath testing (LBT) are common in patients with irritable bowel syndrome (IBS), although the criteria for abnormal studies are poorly validated, and controlled comparisons are limited. The goal of this study was to determine the prevalence of abnormal LBT using the previously published criteria in both IBS patients and healthy controls, as well as to determine the prevalence and symptom association with methane (CH4) and hydrogen (H2) productions during LBT.

Methods: Consecutive LBT from patients meeting Rome II criteria for IBS and healthy control subjects were examined. Patients listed their most bothersome digestive symptom at the start of the test. LBT was performed using 10 g of lactulose mixed in 240 mL of water, and breath samples collected every 20 min for a 180-min period. Both breath H2 and CH4 were measured. LBT was considered positive if it met any of the previously published criteria: (a) breath H2 of >20 parts per million (ppm), (b) increase in breath H2 in <90 min, (c) dual H2 peaks (12-ppm increase over baseline with a decrease of =5 ppm before 2nd peak), and (d) breath CH4 of >1 ppm.

Results: In total, 224 patients with IBS and 40 controls were studied.

Conclusions: The majority of patients with IBS and healthy subjects meet criteria for an “abnormal” LBT using previously published test criteria, and groups are not discriminated using this diagnostic method. Similarly, while CH4 production was associated with constipation among IBS patients, the prevalence of CH4-positive subjects did not significantly differ between IBS patients and controls.

The utility of lactulose breath testing, in its current form as a diagnostic tool in IBS requires critical reappraisal.

Source: American Journal of Gastroenterology. April 2008;103(4)pp 958-963. PMID: 18371134, by Bratten JR, Spanier J, Jones MP. Division of Gastroenterology, Northwestern University, Chicago, Illinois.