Q&A: New breath test adds hydrogen sulfide to better understand the microbiome in patients
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Recently, the small intestine bacterial overgrowth breath test was launched by Cedars-Sinai to diagnose small intestine bacterial overgrowth related to irritable bowel syndrome.
Healio Gastroenterology spoke with Mark Pimentel, MD, executive director of the medically associated science and technology (MAST) program at Cedars-Sinai, on how GIs can use the breath test and what this new device means for patient care.
SIBO breath test was launched by Cedars-Sinai to diagnose small intestine bacterial overgrowth related to IBS.
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Healio: How do general GIs use the SIBO breath test?
Pimentel: Diagnosis of small intestine bacterial overgrowth is quite common and has become better recognized in the last 10 or so years partly because the tools for diagnosing are improving. So, it's quite commonly used; there may be as many as 1,000 breath tests a day done in the United States.
Healio: How is the SIBO breathing test being used in clinics since the launch?
Pimentel: Currently the device is located in the clinical laboratory improvement amendments, or CLIA, certified laboratory of Gemelli Biotech. They have launched a kit-based testing so doctors can order a breath test and then they'll get the kit to the patient. Then, the patient will send it in, and the results will be reported to the doctor. The novelty of the new test is that it adds hydrogen sulfide to other breath gases measured during conventional clinical breath test systems.
Healio: What does this breath test mean for patient care?
Pimentel: We don't have an easy way to diagnose microbiome disease. Our work at Cedars these last 20 years was trying to, first of all, validate breath testing. Breath testing prior to contemporary research really hasn't dissected what the breath test means. So for example, just this year we published a very important paper where we compared a breath test to actual sampling of the small intestine and we were able to prove the hydrogen sulfide criteria on breath test that truly represents bacterial overgrowth.
Our group and now many others have also been instrumental in demonstrating that methane on breath test is associated with constipation and that treating methane could improve constipation. So that's the second leg of the three legged chair of breath testing and its relationship to the microbiome and how it could help humans. The third leg of the chair, and the only other gas that wasn't measured, was hydrogen sulfide. Hydrogen sulfide can have toxic effects on the intestinal lining and so it was always believed that hydrogen sulfide could potentially be associated with diarrhea symptoms in patients, especially in functional GI disorders. We were able to prove now in a series of studies that hydrogen sulfide does that; it is associated with diarrhea. So, in summary, Hydrogen is now an important gas associated with bacterial overgrowth. Methane is now a validated a marker for constipation. Now, hydrogen sulfide could be a marker for diarrhea. The next step is trying to figure out what treatments work for each of these legs of the chair.
Perspective
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Florian Rieder, MD
Breath tests to diagnose or monitor human diseases are highly attractive due to their non-invasive nature. In recent years, great progress has been made to standardize and validate breath testing. One important disorder that allows breath testing is SIBO with or without relation to IBS. This disorder may be related to an altered microbiome leading to symptoms such as bloating and diarrhea. The novel test kit described in this article, aside from being non-invasive, has the added advantage of being able to be performed in the patient’s home and at the patient’s convenience. It incorporates a novel gas, called hydrogen, that appears to be important in SIBO and may enhance accuracy of its diagnosis. Of note, the breath gases seem to reflect what is happening at the level of the gut and they may show pathogenetic relevance, in case of hydrogen a relation with diarrhea due to damage of the intestinal lining. Another validated example is the gas methane and its relation with constipation. The area of breath testing is evolving and exciting. It represents an area where a non-invasive test can provide not only an accurate diagnosis but also clues to disease mechanisms and future therapies. Future studies using unbiased measurement techniques, such as single ion flow tube mass spectrometers, may further expand the universe of breath testing in health and disease.
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