Everything You Need to Know About SIBO Testing
Small Intestinal Quantitative Culture
For many years, the “gold standard” for diagnosing SIBO was small-bowel aspiration and quantitative culture. This involves undergoing an upper endoscopy, where a scope is inserted via the mouth down to the small intestine, and a sample is taken through a sterile catheter using a small amount of suction. The aspirate is typically taken from the jejunum, and is then cultured.
While new sampling techniques have been able to sidestep contamination issues, (Cedar’s Sinai has the technology to do so) quantitative culture comes with it’s own inaccuracies. The issue being that most species that live in the gut are anaerobic, and thus cannot be effectively cultured. The number of colony-forming units (CFU) detected in a sample will depend on whether the microbes in a given individual’s gut can be effectively grown in culture and in the particular growth media chosen.
SIBO Breath Test
There are three types of breath tests that might be used in a patient with SIBO, with the lactulose breath test being the most commonly used test within the integrative or functional medicine communities. Each test comes with it’s own pro’s and cons, and propensity for false negatives or positives.
1.Lactulose Breath Test
Clinical trials evaluating the efficacy of lactulose breath tests have found that they can deliver a false positive up to 44% of the time. This happens because lactulose is a laxative. It can speed up transit time, which means it makes it’s way through the small intestine and into the large intestine faster than the 120 minute mark, giving us test results that reflect large intestinal gas production instead of small. [1]
It is normal for bacteria in the large intestine to feed on the lactulose. This is generally not a negative thing.
If the lactulose is working as planned it can give you a good indication of what’s going on in the distal portion of the small intestine. This is where SIBO typically resides.
2. Glucose Breath Test
The second breath test option is the glucose breath test. Per clinical research evaluation the glucose breath test only has a 13% false positive rate. [2] However, because glucose is absorbed in the small intestine it is only reflective of SIBO in the proximal portion of the small intestine. If you only use the glucose test, and your SIBO is in the distal part of the small intestine, you may end up with a false negative.
3. Fructose Breath Test
I wanted to mention the fructose breath test as well, given that it is occasionally used by SIBO practitioners. The hydrogen breath test using fructose substrate can be used to detect fructose malabsorption, in which case microbes would ferment the fructose into hydrogen.
Those with a positive lactulose test may be more likely to have a positive fructose test, however, you do not need to have a SIBO or IBS diagnosis to have fructose intolerance.
That said, the issue most frequently cited in the literature is that too much fructose is used with breath testing. Almost all healthy subjects can absorb up to 25g, while 75% will malabsorb if 50g is used. We want to make sure that when using these tests not to use more than 25g.
Similar issues were found with sorbitol.
If a patient were unable or did want to use fructose breath testing, one could instead do an elimination and reintroduction of fructose to test response to this specific FODMAP.
General Issues With The Breath Test
Research has found that oral dysbiosis – or microbial overgrowth within the mouth – can cause a false positive on the breath test. Erdrick et al found that administration of a chlorhexidine mouthwash resulted in reduced breath hydrogen in 67% and/or methane gas in 93% of participants.
This is why we have a special non toxic version of this protocol for our clients to account for this and to prevent false positives. [5]
The next issue with breath testing is that most labs do not have a test available that is specific to hydrogen sulfide gas – the third SIBO gas. Quite a few of the microbes correlated with SIBO – Klebsiella, Citrobacter, E-coli, Pseudomonas – can and do produce hydrogen sulfide.
Banik et al. assessed breath excretion of both hydrogen and hydrogen sulfide after ingestion of 50 grams of glucose and performed jejunal aspiration and quantitative culture in 151 patients with diarrhea-predominant IBS. [6] They found that many glucose breath test results that would be considered negative for hydrogen were positive for hydrogen sulfide, and that hydrogen sulfide production was able to predict which individuals were positive for SIBO.
Hydrogen sulfide overgrowth will sometimes be depicted by a flatline. In our SIBO Ecology Method Program we cover how to identify a true flatline.
That said, a number of the hydrogen sulfide producing microbes are easily detectable with a quantifiable culture or PCR test and we encourage going that route.
Finally, the occurrence of false positives is as frequent as 44% of the time for lactulose breath testing and 13% for glucose.
False-positive results may be caused by not following the test preparation and collection guidelines (for example, smoking, sleeping or eating during the test or one hour before the test). Most false-negative tests can be avoided by testing for methane, for which a false positive result is usually clear as day. However, there are other situations that may cause false-negative results, such as one or more invalid samples which may lead to a false negative result.
Using Breath Test to Your Advantage
If symptoms improve, but test still says positive do not continue to treat.
Anything below 10 with lack of constipation is negative for methane.
Make sure to account for the oral microbiome.
Pair your test with a PCR and/or culture.
Know that every substrate feeds a different set of microbes. So glucose prompting a raise in hydrogen is reflective of different types of overgrowth than lactulose prompting a raise in hydrogen. The same applies for methane and the different substrates.
The Future of Testing
Intraluminal Gas Sampling
In April of 2018, a group of Australian researchers published a pilot study of a new telemetric capsule that is swallowed, travels through the GI tract, and can provide real-time measurement of the major gases in the GI tract. The concentration of oxygen allows the capsule to be accurately localized to the stomach, small intestine, or colon, while the concentrations of hydrogen and methane reflect microbial fermentation. Incredibly, the device detected concentrations of hydrogen that were 3000 times higher than those currently detected by breath tests! [9]
Organic Acid Testing for SIBO
Organic acids testing (OAT) is sometimes used by gut health experts as a replacement for SIBO testing. The markers on OAT tests are more specific than what is detected by SIBO breath tests. If you are on a budget and trying to prioritize testing, organic acids testing will be more useful if you are also looking to test for Candida and work through detox pathway issues. The Nutreval is our preferred OAT.
References
[1] Yu, D., Cheeseman, F. & Vanner, S. Combined oro-caecal scintigraphy and lactulose hydrogen breath testing demonstrate that breath testing detects oro-caecal transit, not small intestinal bacterial overgrowth in patients with IBS. Gut 60, 334–340 (2011).
[2] Lin, E. C. & Massey, B. T. Scintigraphy Demonstrates High Rate of False-positive Results From Glucose Breath Tests for Small Bowel Bacterial Overgrowth. Clinical Gastroenterology and Hepatology 14, 203–208 (2016).
[3] Simrén M, Stotzer PO. Use and abuse of hydrogen breath tests. Gut. 2006;55(3):297-303. doi:10.1136/gut.2005.075127
[4] Erdogan A, Adame EC, Yu S, Rattanakovit K, Rao SS. Optimal Testing for Diagnosis of Fructose Intolerance: Over-dosage Leads to False Positive Intolerance Test. J Neurogastroenterol Motil. 2014;20(4):560. doi:10.5056/jnm14085
[5] Erdrich, S., Tan, E.C.K., Hawrelak, J.A. et al. Hydrogen–methane breath testing results influenced by oral hygiene. Sci Rep 11, 26 (2021). https://doi.org/10.1038/s41598-020-79554-x
[6] Banik GD, De A, Som S, Jana S, Daschakraborty SB, Chaudhuri S, Pradhan M. Hydrogen sulphide in exhaled breath: a potential biomarker for small intestinal bacterial overgrowth in IBS. J Breath Res. 2016 May 10;10(2):026010. doi: 10.1088/1752-7155/10/2/026010. PMID: 27163246.
[7] Romagnuolo J, Schiller D, Bailey RJ. Using breath tests wisely in a gastroenterology practice: an evidence-based review of indications and pitfalls in interpretation. Am J Gastroenterol 2002; 97:1113–1126.
[8] Siebecker A, Sandberg-Lewis S. The finer points of diagnosis, test interpretation, and treatment. Naturopathic Doctor News and Review, January 2014, 10:46. http://ndnr.com/gastrointestinal/sibo/
[9] Berean KJ, Ha N, Ou JZ, Chrimes AF, Grando D, Yao CK, Muir JG, Ward SA, Burgell RE, Gibson PR, Kalantar-Zadeh K. The safety and sensitivity of a telemetric capsule to monitor gastrointestinal hydrogen production in vivo in healthy subjects: a pilot trial comparison to concurrent breath analysis. Aliment Pharmacol Ther. 2018 Sep;48(6):646-654. doi: 10.1111/apt.14923. Epub 2018 Aug 1. PMID: 30067289.
