For years, SIBO breath testing had a blind spot. Standard tests measured hydrogen and methane but had no way to detect hydrogen sulfide, the third gas produced by bacterial overgrowth. The trio-smart breath test changed that. Developed by Gemelli Biotech in collaboration with Dr. Mark Pimentel's team at Cedars-Sinai, it is the first and currently only commercially available breath test that measures all three SIBO-associated gases. For patients who have tested negative on standard breath tests despite classic SIBO symptoms, and especially for those with the telltale flat-line hydrogen pattern, the trio-smart test fills a critical diagnostic gap.
What trio-smart measures versus standard tests
Standard lactulose and glucose breath tests measure two gases: hydrogen (H2) and methane (CH4). The devices used in most gastroenterology offices and home test kits detect these gases through electrochemical sensors. They have no capability to measure hydrogen sulfide. The trio-smart test uses a proprietary device with an additional sensor specifically calibrated to detect hydrogen sulfide at parts-per-million concentrations in exhaled breath. This matters because hydrogen sulfide is present at much lower concentrations than hydrogen or methane, requiring more sensitive detection technology. The test produces a three-gas reading at each time point, giving a complete picture of which bacterial populations are active and producing gas.
Who should get a trio-smart test?
- Patients with classic SIBO symptoms (bloating, diarrhea, gas, brain fog) who tested negative on a standard two-gas breath test.
- Patients whose standard breath test showed a flat-line hydrogen pattern (hydrogen remaining below 10-15 ppm throughout the test), which is a hallmark signature of hydrogen sulfide SIBO.
- Patients with sulfur-specific symptoms: sulfur-smelling gas or burps, sensitivity to sulfur-rich foods (eggs, garlic, onions, cruciferous vegetables), and diarrhea with urgency.
- Patients who have been treated for hydrogen or methane SIBO but continue to have symptoms, suggesting a missed H2S component.
- Patients being tested for SIBO for the first time who want the most comprehensive initial evaluation available.
How to prepare for the test
Preparation for the trio-smart test follows a similar protocol to standard breath testing, with strict adherence important for accurate results. For 24 hours before the test, you follow a preparation diet limited to white rice, plain baked or broiled chicken or fish (unseasoned), eggs (plain, no butter or oil), clear beef or chicken broth, and water. This low-fermentation diet clears residual fermentable substrates from the intestine so that the test substrate (lactulose) is the only material available for bacterial fermentation. Avoid all high-FODMAP foods, fiber, dairy, legumes, sugar alcohols, and complex carbohydrates during the preparation period.
After the 24-hour diet, you fast for 12 hours overnight before the test (water is typically allowed during the fast). On the morning of the test, do not eat, drink (other than a small amount of water), smoke, exercise, or chew gum. Certain medications should be stopped before the test: antibiotics (4 weeks before), prokinetics (3 days before), laxatives (3 days before), and antacids (12 hours before). Consult your ordering physician about any medication holds, especially if you take medications that cannot be safely interrupted.
What happens during the test
The trio-smart test is completed at home using a kit shipped to you after your physician places the order. The kit contains a lactulose solution (the test substrate), collection tubes, and detailed instructions. You provide a baseline breath sample before drinking the lactulose solution. Then you collect breath samples at regular intervals (typically every 15-20 minutes) for a total of 2-3 hours. Each collection involves exhaling into a tube through a one-way valve. The samples are then shipped back to the laboratory using a prepaid shipping label. Results are typically available to your ordering physician within 5-7 business days and include hydrogen, methane, and hydrogen sulfide readings at each time point, plotted on a graph.
âšī¸Timing is important during the collection. Set alarms for each sample to avoid missing or delaying a collection. Late samples can shift the gas curves and affect interpretation, particularly the 90-minute cutoff used for hydrogen assessment.
Interpreting three-gas results
The trio-smart results show three gas curves plotted over time. Positive thresholds are based on established consensus criteria. Hydrogen is positive if it rises 20 ppm or more above baseline within 90 minutes. This indicates hydrogen-producing bacterial overgrowth in the small intestine. Methane is positive at 10 ppm or more at any point during the test. This indicates intestinal methanogen overgrowth (IMO), which is associated with constipation-predominant symptoms. Hydrogen sulfide is positive at 3 ppm or more at any point during the test. This indicates sulfate-reducing bacterial overgrowth and is associated with diarrhea, sulfur symptoms, and often brain fog.
Multiple gases can be elevated simultaneously. A patient might show elevated hydrogen and hydrogen sulfide (indicating hydrogen-producing bacteria feeding sulfate-reducers), or elevated methane and hydrogen sulfide (indicating both methanogens and SRB are present). The specific gas pattern helps guide treatment: hydrogen-dominant SIBO is typically treated with rifaximin alone, methane-dominant with rifaximin plus neomycin or metronidazole, and hydrogen sulfide-dominant with rifaximin plus bismuth subsalicylate. Mixed presentations may require combination approaches.
The flat-line hydrogen pattern explained
One of the most important patterns to recognize is the flat-line hydrogen result, where hydrogen remains below 10-15 ppm throughout the entire test. On a standard two-gas test, this looks like a clear negative result. On trio-smart, these patients often show elevated hydrogen sulfide, revealing that hydrogen is being produced but immediately consumed by sulfate-reducing bacteria before it can reach the breath. Singer-Englar et al. (2022) demonstrated that this flat-line hydrogen pattern is a specific marker of hydrogen sulfide SIBO. If you received a flat-line result on a previous standard test and your clinician dismissed it as negative, a trio-smart retest is strongly warranted.
What to do with your results
A positive trio-smart result for any gas confirms bacterial overgrowth and identifies which type (or types) you have. Share the full results with your treating physician, ideally one experienced in SIBO management. The gas-specific results directly inform treatment selection. For hydrogen sulfide positivity, treatment protocols typically include rifaximin with the addition of bismuth subsalicylate to target sulfate-reducing bacteria. Dietary sulfur restriction may help manage symptoms during and after treatment. If the underlying root cause of SIBO (impaired motility, low stomach acid, structural issues) is not addressed, retesting after treatment helps confirm eradication and catch early recurrence.
â ī¸This article is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about a medical condition.