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WHAT IS BREATH TESTING?
Breath testing is a way for healthcare providers to identify certain conditions related to the gut microbiome by analyzing fermented gases in patients’ exhaled breath. The three primary fermented gases found in the gut microbiome are hydrogen, methane, and hydrogen sulfide. While healthy levels of all three gases can be present in the gut microbiome, abnormal levels can indicate a disorder and provide valuable insight into proper treatment
Intestinal overgrowth (SIBO, IMO, and excess hydrogen sulfide) breath testing measures levels of hydrogen, methane, and hydrogen sulfide after a patient consumes lactulose or glucose. Abnormal levels of hydrogen, methane, or hydrogen sulfide can indicate small intestinal bacterial overgrowth (SIBO), intestinal methanogenic overgrowth (IMO), and/or the presence of excess hydrogen sulfide. After the sugar substrate drink is consumed, the bacteria in the gut eat the sugar and release specific gases. If there is an overgrowth of bacteria, excess gas will be produced, which is detectable with a breath test. There is only one breath test, trio-smart, that can measure all three of the gases associated with SIBO, IMO, and excess hydrogen sulfide.
trio-smart is a doctor-ordered mail-in breath test used to measure the three primary fermented gases in the microbiome - hydrogen, methane, and hydrogen sulfide - associated with conditions like SIBO, IMO, and excess hydrogen sulfide.
WHEN SHOULD A BREATH TEST BE CONSIDERED?
Patients experiencing the following gastrointestinal symptoms once a week or more for at least four weeks are most likely to benefit from a breath test:
The most prominent symptom of SIBO is bloating. Patients with irritable bowel syndrome and suspected motility disorders may be especially fit for breath testing.
While breath testing can help providers identify the root cause of a patient's symptoms, breath testing is often used to assess treatment efficacy, as well. Therefore, providers may wish to prescribe a breath test before, during, and/or after treatment.
WHAT DOES A BREATH TEST DETECT?
Breath testing is a tool to evaluate gases produced in the gut microbiome by analyzing an exhaled breath sample. Common gases measured are:
Carbon Dioxide (CO2)
Hydrogen Sulfide (H2S)
It’s important to note that there are specific symptoms and conditions linked to abnormal levels of each gas. The three primary fermented gases found in the gut microbiome are hydrogen, methane, and hydrogen sulfide. Each gas is associated with a gastrointestinal condition.
Hydrogen is produced when certain bacteria in the small intestine consume sugars and produce hydrogen gas as a byproduct. Elevated levels of hydrogen are indicative of Small Intestinal Bacterial Overgrowth (SIBO).
Methane is produced when archaea (single-celled organisms similar to bacteria) consume hydrogen. Elevated levels of methane are indicative of Intestinal Methanogenic Overgrowth (IMO) and are associated with constipation. The level of methane is correlated with the degree of constipation.
Hydrogen sulfide is produced when hydrogen sulfide-producing organisms consume hydrogen. Elevated levels of hydrogen sulfide are indicative of excess hydrogen sulfide and are associated with diarrhea. The level of hydrogen sulfide is correlated with the degree of diarrhea.
Learn more about SIBO, IMO, and excess hydrogen sulfide here.
HOW ARE BREATH TEST RESULTS REPORTED?
While results may look different from one breath testing provider to the next, they will often contain a graph reporting the levels of each gas over time. Reports will also indicate any gases that are elevated abnormally. Each gas has its own established threshold between “normal” and “abnormal.”
See a sample report from trio-smart here.
The trio-smart breath test is performed by measuring levels of Hydrogen (H2), Methane (CH4), and Hydrogen Sulfide (H2S) in the breath of patients collected every 15 minutes after lactulose or glucose consumption.
trio-smart follows the recommendations provided by the North American Consensus on Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders.
HYDROGEN: The threshold of hydrogen is calculated by adding 20 ppm to the baseline. A rise in hydrogen levels by 20 ppm or more within 90 minutes is supportive of SIBO.
METHANE: The threshold for methane is always 10 ppm. Levels of methane that are 10 ppm or more at any point during the breath test are considered abnormal. Elevated levels are associated with constipation.
HYDROGEN SULFIDE: The threshold for hydrogen sulfide is always 3 ppm. Levels of hydrogen sulfide that are 3 ppm or more at any point during the breath test are considered excess and are associated with diarrhea.
HYDROGEN, METHANE, AND HYDROGEN SULFIDE DO NOT ACT INDEPENDENTLY.
Hydrogen, methane, and hydrogen sulfide interact with each other in a complex way. Hydrogen is produced by fermenting bacteria but is also consumed by other organisms, resulting in the production of other gases, including methane and hydrogen sulfide.
There is a balance-counterbalance effect between methane and hydrogen sulfide, illustrating a biochemical interdependency between microbes in the microbiome. These findings are important, because they indicate limitations when measuring only one or two of the three primary fermented gases.
THREE-GAS BREATH TESTING
Prior to the breakthrough three-gas breath testing technology of trio-smart, testing for bacterial overgrowth was limited to the measurement of only two of the three primary fermented gases: hydrogen and methane.
Hydrogen sulfide is important to measure, because it is the only gas strongly associated with diarrhea, with the level of hydrogen sulfide correlating with the degree of diarrhea. Hydrogen sulfide was previously undetectable, so patients with elevated hydrogen sulfide often went unrecognized by one-gas or two-gas breath tests.
Measuring hydrogen and methane can offer a partial story about a patient’s GI symptoms. With a three-gas breath test, all three primary fermented gases in the microbiome - hydrogen, methane, and hydrogen sulfide - can be measured, offering the most complete picture.
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Rezaie, A., Buresi, M., Lembo, A., Lin, H., McCallum, R., Rao, S., Schmulson, M., Valdovinos, M., Zakko, S., & Pimentel, M. Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus. American Journal of Gastroenterology, 2017.
Lacy, B., Pimentel, M., Brenner, D., Chey, W., Keefer, L., Long, M., & Moshiree, B. ACG Clinical Guideline: Management of Irritable Bowel Syndrome. The American Journal of Gastroenterology, 2021.
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Pimentel, M., Mathur, R., & Chang, C. Gas and the Microbiome. Current Gastroenterology, 2013.
Singer-Englar, T., Rezaie, A., Gupta, K., Pichetshote, N., Sedighi, R., Lin, E., Chua, K., & Pimentel, M. Validation of a 4-Gas Device for Breath Testing in the Determination of Small Intestinal Bacterial Overgrowth. AGA Abstracts, 2018.