Testing for SIBO

Small intestinal bacterial overgrowth (SIBO) is a common problem that often goes undiagnosed. Misdiagnosis occurs due to the complexity of the condition, which requires a customized approach to treatment including appropriate supplementation, exercises to strengthen the parasympathetic nervous system — which is responsible for the brain–gut connection — and nutritional counseling.

Some symptoms of SIBO include abdominal bloating, gas, diarrhea, and constipation, but these symptoms alone do not predict a positive diagnosis. SIBO can be properly diagnosed through the patient’s medical history, current symptoms, and a variety of lab tests.

Why symptoms alone aren’t enough

While symptoms alone don’t provide a conclusive diagnosis, keeping track of them is an important first step toward getting an accurate diagnosis. Symptoms of SIBO include:

• Increasing food intolerances
• Flatulence / bloating
• Abdominal swelling
• Abdominal pain
• Nausea
• Acid reflux
• Acne / skin conditions
• Fatigue
• Diarrhea / constipation
• Brain fog
• Headaches
• Depression / anxiety
• Body aches and pain

Non-invasive lab tests for SIBO include DNA stool tests that measure bacteria and fecal fat, and breath tests that measure hydrogen and methane. Each of these tests provides important information about the gastrointestinal system to help diagnose SIBO. Together, they can provide a more accurate diagnosis.

DNA stool testing

The GI-MAP for bacteria

A DNA stool test requires a stool sample to measure gas-producing opportunistic bacteria that can cause digestive issues such as gas and bloating in people with SIBO. At Genesis Functional Wellness, we successfully diagnose many SIBO patients using the GI-MAP DNA stool test. The GI-MAP measures a wide range of opportunistic bacteria that are indicative of SIBO and are generally recognized to overproduce in the small intestine. However, the test cannot determine if the bacteria are actually from the small intestine or the large intestine, as bacteria are passed from one to the other.

The GI-MAP measures three different types of bacteria that can cause SIBO:

• Methanobacteriaceae form methane gas. High levels may indicate methane-dominant SIBO.
• Hydrogen-producing bacteria — Bacillus spp., Enterococcus faecalis, Enterococcus faecium, Staphylococcus spp., and Streptococcus spp. High levels may indicate hydrogen-dominant SIBO.
• Hydrogen sulfide–forming bacteria — Citrobacter spp., Proteus spp., and Fusobacterium spp. High levels may indicate sulfide-dominant SIBO and/or SIFO (small intestinal fungal overgrowth), which can also cause GI symptoms.

Steatocrit (fecal fat)

With SIBO, opportunistic bacteria that invade the small intestine compete for nutrients with the normal bacteria of the small intestine. This can lead to malabsorption of nutrients, altered metabolism, damage to the absorptive lining of the GI system, and gastrointestinal symptoms (1). The GI-MAP also measures steatocrit, or fecal fat (2). Elevated steatocrit indicates malabsorption of fat and also suggests SIBO.

Breath testing

Non-invasive breath testing is widely available. However, it is an indirect method that requires further standardization and validation for SIBO. Though less specific than other types of tests for diagnosing bacterial overgrowth, it can be used in combination with other tests to provide a more accurate diagnosis (3).

There are two types of non-invasive breath tests that can be done at home. Each one measures the amount of a specific gas exhaled in the breath after drinking a sugary liquid. Since the gas in your colon is absorbed into your bloodstream, carried into your lungs, and released from your body through your breath, a rapid rise in hydrogen (H2), methane (CH4), and/or hydrogen sulfide (H2S) in the breath may indicate bacterial overgrowth in your small intestine (4).

The more traditional lactulose breath test uses a synthetic sugar called lactulose as a testing agent. It is very effective in measuring hydrogen and methane, which are both indicative of SIBO. However, it isn’t as effective in measuring hydrogen sulfide, which is also indicative of SIBO and/or SIFO (small intestinal fungal overgrowth).

At Genesis Functional Wellness, we prefer to use the newer Trio-Smart breath test, which not only tests for hydrogen (H2) and methane (CH4) but also for hydrogen sulfide (H2S).

A simple at-home test

FODMAP is an acronym for Fermentable Oligo-, Di-, and Monosaccharides, and Polyols. These short-chain carbohydrates draw water into the digestive tract, causing gastrointestinal symptoms such as cramping, bloating, burping, and diarrhea. They are also fermented rapidly by gas-producing bacteria, which increases the intensity of GI symptoms (5). Individuals with SIBO are sensitive to foods with a high FODMAP content and usually burp or bloat within 30 minutes to several hours after eating these foods. To do a simple at-home test, eat a high-FODMAP food in singular form and note how you respond.

Small-bowel aspiration

Recent American College of Gastroenterology guidelines endorsed small-bowel aspiration as the best technique for identifying SIBO. Though most GI experts agree on its accuracy, small-bowel aspiration is invasive, costly, and still needs to be standardized (6). While this procedure seems promising and may provide the most accurate diagnosis of SIBO, the test is not widely used yet, and it isn’t an essential tool for a practitioner who is experienced with diagnosing and treating SIBO.

Here’s how the procedure works: during the aspiration procedure, an endoscope is inserted into the esophagus while the patient is under sedation. Fluid from the duodenum, the first part of the small intestine, is removed and sent to the lab, where bacterial and fungal levels are measured.

SIBO is a complex condition that can be properly diagnosed through a variety of tests. Symptoms, while not conclusive, are an important part of the diagnostic process. At Genesis Functional Wellness, we can prescribe the appropriate tests for you and customize a treatment plan to meet your specific needs.