Diagnosing Small Intestinal Bacterial Overgrowth: A Comparison of Lactulose Breath Tests to Small Bowel Aspirates

Duodenal aspiration (DA) and lactulose breath tests (LBT) are commonly performed to diagnose small intestinal bacterial overgrowth (SIBO). There are no data directly comparing these tests.

To investigate the agreement between DA and LBT for the diagnosis of SIBO.

A retrospective cohort study of adult patients who underwent a LBT and a DA at a tertiary care center over 9 years was assembled. LBT was considered positive if the hydrogen baseline or peak change measurement was ≥ 20 ppm, and/or if the methane baseline or peak change was ≥ 10 ppm. DA was considered positive if > 100,000 cfu/mL of gram-negative flora was identified on culture, and contaminated if > 100,000 cfu/mL of gram-positive flora was identified.

A total of 106 patients were evaluated; 81 (76.4%) were female; the mean age was 53.4 ± 15.9 years. 21 patients (19.8%) had evidence of contamination on DA. 14 (16.5%) patients had a positive DA result. Patients with diabetes mellitus and those with PPI use were more likely to have a positive DA (94.4% vs. 71.4%, p = 0.007; 62% vs. 28.6%, p = 0.021, respectively). 33 (31.1%) patients had a positive LBT. Patients with a history of small bowel resection were more likely to have a positive LBT (12.1% vs. 1.4%, p = 0.016). DA and LBT results agreed in 54 patients (63.5%; kappa = - 0.02), indicating poor agreement.

The agreement between LBT and DA in evaluation for SIBO was poor. LBT may be favorable to DA, as LBT is safer, cheaper, and less likely to yield a contaminant result.