The diagnosis of small intestinal bacterial overgrowth (SIBO) has increased considerably owing to a growing recognition of its association with common bowel symp- toms including chronic diarrhea, bloating, abdominal distention, and the irritable bowel syndrome. Ideally, an accurate and objective diagnosis of SIBO should be estab- lished before initiating antibiotic treatment. Unfortunately, no perfect test exists for the diagnosis of SIBO. The current gold standard, small-bowel aspiration and quantitative culture, is limited by its high cost, invasive nature, lack of standardization, sampling error, and need for dedicated infrastructure. Although not without shortcomings, hydrogen breath testing provides the simplest noninvasive and widely available diagnostic modality for suspected SIBO. Carbohydrates such as lactulose and glucose are the most widely used substrates in hydrogen breath testing, with glucose arguably providing greater testing accuracy. Lactose, fructose, and sorbitol should not be used as sub- strates in the assessment of suspected SIBO. The mea- surement of methane in addition to hydrogen can increase the sensitivity of breath testing for SIBO. Diagnostic accu- racy of hydrogen breath testing in SIBO can be maximized by careful patient selection for testing, proper test prepa- ration, and standardization of test performance as well as test interpretation.

Keywords: Small Intestinal Bacterial Overgrowth; Hydrogen Breath Test; SIBO; Glucose Hydrogen Breath Test; Lactulose Hydrogen Breath Test.