Table.

Strengths and Limitations of Breath Testing

Strengths

Exhaled breath hydrogen and methane are exclusive biomarkers of metabolically active gut microbes

Safe, simple, and noninvasive

Widely accessible and inexpensive with home testing option

Antibiotic therapy can be tailored based on breath test patterna

Breath testing is the only diagnostic test for IMO IMO test results are not affected by OCTT

Spot methane measurement is a rapid point-of-care method to diagnosis IMO and assess treatment response

Lactulose breath test can help identify patients with diarrhea-predominant irritable bowel syndrome who are more likely to be rifaximin responders

Limitations

Indirectly measures microbial overgrowth

Accuracy of result relies on patient compliance to protocol: Oral care Avoid exercise or smoking on day of test Avoid fermentable foods on day prior to test No antibiotics 4 weeks before test Discontinuation of promotility agents or laxatives 1 week before test Avoid colonoscopy bowel preparation at least 2 weeks before test

Various commercial home tests: May use thresholds for breath hydrogen and methane that are different from cutoffs outlined in clinical guidelines May include a combined criteria of hydrogen and methane, which are not supported by data and can lead to false-positive results

Low breath hydrogen can occur when excessive methanogens and hydrogenotrophic bacteria are present

SIBO test results can be affected by variations in OCTT: Rapid OCTT can result in false-positive result Slow OCTT can result in false-negative result

Conditions that impair delivery of the carbohydrate substrate to the small intestine can result in false-negative results (ie, gastroparesis, gastric outlet obstruction, achalasia, and enterocutaneous fistula)

^aHydrogen-predominant SIBO treatment: rifaximin; IMO treatment: rifaximin/neomycin, rifaximin/flagyl, or ciprofloxacin/flagyl.

IMO, intestinal methanogen overgrowth; OCTT, orocecal transit time; SIBO, small intestinal bacterial overgrowth.