By Sarah Bloor, Clinical GI Physiologist
Understanding your SIBO report
In an individual with SIBO, there will be a rise of hydrogen gas within the first 90 minutes of the study. A rise in hydrogen during this period doesn’t mean an automatic SIBO diagnosis as the natural low level of bacteria in the small intestine will produce low levels of hydrogen. Therefore, to get a positive SIBO diagnosis, there must be a rise above baseline levels of 10ppm of hydrogen in 60 minutes, or 20ppm of hydrogen in 90 minutes. There are two cut off values to determine a positive result, different guidelines defined both, the 60 minute cut off is the European (Eisenmann at al., 2008) and the 90 minute cut off by a North American Consensus (Rezaie et al., 2017).
There are two cut off values for a positive SIBO diagnosis because there is a lot of uncertainty around the best cut off for SIBO. The European guidelines are more conservative and more likely to decrease the number of false positive results. In contrast the North American guidelines are more likely to have false positives as it is believed that in about half of people the lactulose will be in the colon by 90 minutes (Paterson et al., 2017). To get an accurate diagnosis, the Association of Gastrointestinal Physiologists (AGIP) recommend interpreting symptom data from the patients study in-line with gas production to help support a positive SIBO diagnosis (AGIP, 2019). Therefore, we include both guidelines to allow your consultant to make the best decision as to your next steps. We also correlate your gas production to symptoms to support your diagnosis and ensure you get the correct diagnosis.
Whilst methane isn’t used in the SIBO diagnosis, it can indicate an imbalance in gut microbiome. Low levels of methane are common in healthy individuals, however high levels of methane (>10ppm) have been associated with constipation and bloating. Methane isn’t produced by bacteria, but by methanogens, which are a type of archaea and use the hydrogen produced by bacterial fermentation to produce methane.
Interpreting results from a SIBO breath test is based on having normal transit. From a breath test, we can identify patients that may have slow gastrointestinal transit and may benefit from a gastric emptying test. We can determine this in a lactulose breath test where the results show a lack of a colonic peak of hydrogen. This is due to indigestible sugar not reaching the colon where the colonic bacteria ferments it, and hydrogen is detected by the end of the breath test. (Please note that lactulose breath testing is not the gold standard test for assessing transit and is just an estimate. Glucose breath testing cannot be used to assess transit time as it is absorbed).
A lack of a colonic peak may also be due to the presence of hydrogen sulphide producing bacteria, where before the hydrogen gets into the bloodstream it is used to produce hydrogen sulphide. At present, there is no way to detect hydrogen sulphide via breath testing, but it is commonly seen in individuals that have symptoms of diarrhoea and unpleasant smelling wind (AGIP, 2019).
| What We Can Detect | What It Means |
| High baseline hydrogen (>20ppm) | Patient may not have followed the diet, fast and other preparation correctly |
| Increase of 10ppm hydrogen within 60 minutes | SIBO positive by European Consensus |
| Increase of 20ppm hydrogen within 90 minutes | SIBO positive by North American Consensus |
| Increase in hydrogen after 90 minutes | Normal lactulose fermentation by bacteria in the colon (not found in a glucose breath test) |
| A lack of a peak of hydrogen after 90 minutes | Potential slow gastrointestinal transit, or possible hydrogen sulphide production |
| Presence of methane (>10ppm) | Excessive methane production due to methanogen overgrowth |
References
AGIP, 2019. Association of Gastrointestinal Physiologists (AGIP) Proposed Standardised Testing Protocol for Hydrogen/Methane Breath Testing (HMBT) to Assess Small Intestinal Bacterial Overgrowth (SIBO) and Carbohydrate Malabsorption. Available at: <https://www.bsg.org.uk/wp-content/uploads/2019/12/AGIP-Best-Practice-Statement-for-HMBT_24.01.19.pdf> [Accessed 28 Apr. 2020].
Eisenmann, A., Amann, A., Said, M., Datta, B. and Ledochowski, M., 2008. Implementaion and interpretation of hydrogen breath tests. 2.
Gasbarrini, A., Corazza, G.R. and Gasbarrini, G., 2009. Methodology and Indications of H2-Breath Testing in Gastrointestinal Diseases: the Rome Consensus Conference. Alimentary Pharmacology & Therapeutics, 29(s1), pp.1–49.
Paterson, W., Camilleri, M., Simren, M., Boeckxstaens, G. and Vanner, S.J., 2017. Breath Testing Consensus Guidelines for SIBO: RES IPSA LOCQUITOR. Official journal of the American College of Gastroenterology | ACG, 112(12), pp.1888–1889.
Rezaie, A., Buresi, M., Lembo, A., Lin, H., McCallum, R., Rao, S., Schmulson, M., Valdovinos, M., Zakko, S. and Pimentel, M., 2017. Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus. Am J Gastroenterol, 112(5), pp.775–784.
Simren, M. and Stotzer, P.O., 2006. Use and abuse of hydrogen breath tests. Gut, 55(3), pp.297–303.
