5 min|Dr. Maya Kuczma
From Symptoms to Solutions: Navigating SIBO Testing for Gut HealthWellness, Health, Gut Health
Who Should be Tested for SIBO?
Small intestinal bacterial overgrowth (SIBO) is the result of a variety of digestive issues, and in turn, can lead to many symptoms and conditions. If you have SIBO, you may experience the more common symptoms, such as bloating, diarrhea, and/or constipation, or you may experience conditions associated with SIBO, such as IBS or Crohn's, or the wide variety of symptoms known to be linked to SIBO (When Good Bugs Go Bad).
As a result of the large overlap between SIBO symptoms and symptoms of other gut conditions, it is impossible to diagnose based on symptoms alone. Testing to rule SIBO in - or out - is good practice, even if you have already been diagnosed with a digestive condition.
Additionally, if you are experiencing digestive symptoms yet traditional tests such as gastroscopy, colonoscopy, or CT scan have shown normal results, testing for SIBO can be helpful in discovering the cause of functional digestive alterations that may have occurred in the absence of structural damage.
How to test for SIBO?
1) Breath tests
Bacteria and archaea are the only sources of hydrogen and methane in the gut. These gases are typically only produced in the large intestine of healthy individuals(1). In the gut of patients with SIBO, bacteria and/or archaea proliferate and produce these gases in the small intestine. Bacteria and archaea produce these gases by fermenting certain carbohydrates.
During a breath test, the amounts of these gases produced are measured, as well as the timing, after meals, they are produced. The levels of gas, in addition to timing, can indicate if there is a bacterial overgrowth in the small intestine, and whether the abundance of gas is due to solely hydrogen-producing bacteria, methane-producing archaea, or both.
Prior to the test, a 12-hour fast must be completed (no food, but prescription meds and water are allowed). For the 24-hours prior to the fast, a specific diet must be followed in order to decrease exposure to fermentable foods, thereby decreasing chances of a false positive. After the fast is complete, an initial breath sample is taken by breathing into a tube; these measures baseline gas levels.
A lactulose or glucose (carbohydrate) solution is then ingested and subsequent breath samples were taken every 20 minutes, storing the gas the small intestine produces for a total of three hours.Currently, these tests are not standardized; however, accuracy is improved if both methane and hydrogen are measured in order to test for hydrogen-producing bacteria, methane-producing archaea, and specific bacteria that produce methane such as Staphylococcus aureus, and Streptococcus viridan(2, 3, 4).
There are still conflicting thoughts as to whether lactulose or glucose is the ‘best’ substrate to use(5). In a comparison of glucose to lactulose, glucose breath testing was shown to be more specific and sensitive when testing for SIBO(6). Additionally, more false positives were reported when lactulose was used(7). However, there are concerns about the absorption of glucose within the small intestine and how this absorption may interfere with identifying cases of SIBO occurring towards the end of the small intestine(5).
A 3-hour test is considered more reliable than the 1 or 2-hour tests that some laboratories are offering due to the time it takes for gases to travel through all three parts of the small intestine, into the bloodstream, and out through the breath.The breath test is considered the safest, easiest, and most widely accessible testing method. It is relatively cheap, non-invasive, and can be completed at home. However, it does have its limitations.
Breath testing does not currently measure hydrogen sulphide, another gas that plays a role in gut health. Additionally, it is subject to individual error and is highly influenced by diet, smoking, recent use of antibiotics, rapid digestive transit time, as well as exercise(8,9). Lastly, there are currently no set criteria for interpreting breath test results; a patient may be diagnosed positive by one practitioner and negative by another, depending on individual interpretation(10).
2) Small Bowel Aspirate
Historically, the small bowel aspirate was considered the Gold standard for testing for and diagnosing SIBO(11,12). During this test, a tube is placed through the nose, into the stomach, until it reaches the small intestine, where a small amount of fluid is aspirated (removed). This fluid is cultured to determine what bacteria are present. Unfortunately, this test is quite invasive and requires a highly skilled professional to perform it.
Additionally, research indicated that this method only reveals 10% of the microbiota in the small intestine(13). Due to the inconsistent occurrence of SIBO throughout the small intestine, aspirate may fail to adequately measure the overgrowth occurring in other areas of the small intestine, distal to the test site location(14). Lastly, certain bacterial species within the small intestine cannot be effectively cultured(15). For these reasons it has fallen out of favour and is not commonly used in clinical practice to diagnose SIBO.
3) Stool tests
Stool tests can show signs of SIBO such as fat malabsorption and bacterial composition changes in the colon. Additionally, stool testing can be used to rule out parasites, measure inflammation levels in the large intestine, and measure levels of yeast in the large intestine.
However, the environment of the large intestine has very little in common with the small intestine; stool testing can provide us with useful information about the current state of digestion as well as the microbiome of the large intestine but is not considered an accurate test for diagnosing SIBO(16).
4) Urine Organic Acid testing
Testing the urine for organic acids can show signs of systemic yeast/bacteria in the body and indicate the presence of bacterial overgrowth. However, this test cannot show where the bacterial overgrowth is occurring and is therefore not considered to be a specific or accurate test for diagnosing SIBO.
Have you been diagnosed with SIBO? Are you wondering why you developed this condition? (The 9 Causes of SIBO That Has You Struggling)