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

Dig Dis Sci. 2021 Jun;66(6):2042-2050. doi: 10.1007/s10620-020-06484-z. Epub 2020 Jul 17.


Background: 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.

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

Methods: 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.

Results: 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.

Conclusions: 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.

Keywords: Bloating; Duodenal aspirate; Lactulose breath test; Small intestinal bacterial overgrowth.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Bacterial Infections / diagnosis
  • Bacterial Infections / metabolism
  • Biopsy, Needle / methods
  • Blind Loop Syndrome / diagnosis*
  • Blind Loop Syndrome / metabolism*
  • Breath Tests / methods
  • Cohort Studies
  • Duodenum / pathology*
  • Female
  • Humans
  • Intestine, Small / pathology
  • Lactulose / analysis*
  • Lactulose / metabolism*
  • Male
  • Middle Aged
  • Retrospective Studies


  • Lactulose