SIBO Testing
Unfortunately there is no perfect test. The small intestine (SI) is a hard place to get to. If we want to see or sample the SI, endoscopy only reaches into the top portion, and colonoscopy only reaches into the end portion. The middle portion, which is substantial (about 17 feet) is not accessible (other than by surgery or wireless capsule endoscopy). And stool testing predominantly reflects the large intestine. Luckily, there are two non-invasive tests:
- SIBO Breath Test
- IBS Blood Test (anti vinculin/anti-CdtB antibodies)
SIBO Breath Test
A breath test can be used to diagnose several conditions: H pylori infection (the Urea Breath test which tests CO2), carbohydrate malabsorption (ex. lactose) and SIBO.
SIBO Breath Test
Breath testing measures the hydrogen and methane gas produced by bacteria in the small intestine that has diffused into the blood, then lungs, for expiration. Hydrogen and methane are gases produced by bacteria, not by humans. Hydrogen sulfide gas also contributes to SIBO (testing is available from one US lab, Trio Smart). The gases are graphed over 2 or 3 hours & compared to baseline. Patients drink a sugar solution of lactulose or glucose after a 1 day preparatory diet. The prep diet removes much of the food that would feed the bacteria, allowing for a clear reaction to the sugar drink.
Two types of tests may be used: Lactulose or Glucose.
SIBO Breath Test
Breath testing measures the hydrogen and methane gas produced by bacteria in the small intestine that has diffused into the blood, then lungs, for expiration. Hydrogen and methane are gases produced by bacteria, not by humans. Hydrogen sulfide gas also contributes to SIBO (testing is available from one US lab, Trio Smart). The gases are graphed over 2 or 3 hours & compared to baseline. Patients drink a sugar solution of lactulose or glucose after a 1 day preparatory diet. The prep diet removes much of the food that would feed the bacteria, allowing for a clear reaction to the sugar drink.
Two types of tests may be used: Lactulose or Glucose.
Lactulose Breath Test (LBT)
Humans can't digest or absorb lactulose. Only bacteria have the proper enzymes to do this. After bacteria consume lactulose, they make gas. If there is an overgrowth, this will be reflected in the levels of Hydrogen and/or Methane.
The advantage to this test is that it can diagnose overgrowth in the distal end of the SI, thought to be more common. The disadvantage is that it cannot diagnose bacterial overgrowth as well as the Glucose Breath Test (GBT).
In the US lactulose is a prescription which limits its availability. However, two US labs offer direct patient ordering: Direct Labs and True Health Labs.
The advantage to this test is that it can diagnose overgrowth in the distal end of the SI, thought to be more common. The disadvantage is that it cannot diagnose bacterial overgrowth as well as the Glucose Breath Test (GBT).
In the US lactulose is a prescription which limits its availability. However, two US labs offer direct patient ordering: Direct Labs and True Health Labs.
Glucose Breath Test (GBT)
Both humans and bacteria absorb glucose. Glucose is absorbed within the first three feet of the SI, therefore if the bacterial gases of Hydrogen and/or Methane are produced during this test, it reflects an overgrowth in the proximal/upper end of the SI (within the first two feet).
The advantage to this test is that it successfully and accurately diagnoses proximal overgrowth. The disadvantage is that it cannot diagnose distal overgrowth, occurring in the latter 17 feet of the SI, which is thought to be more common.
The advantage to this test is that it successfully and accurately diagnoses proximal overgrowth. The disadvantage is that it cannot diagnose distal overgrowth, occurring in the latter 17 feet of the SI, which is thought to be more common.
How is the test performed?
The test is performed either at home with a take home kit or at a facility that has a breath testing machine such as a hospital, doctors office, or clinic lab. It takes 1-3 hours in the morning after a 12 hour fast the night before and a special diet the day before. At home kits may be obtained from numerous breath testing laboratories.
Which Test Is Best?
Physicians and studies use both glucose and lactulose. I currently use the 3 hour lactulose test and have good results with this method.
Newly available in the US, (Sep 2020) is a lactulose 3-gas test (Trio Smart), which measures hydrogen sulfide, in addition to hydrogen and methane, offering the most comprehensive SIBO assessment.
Newly available in the US, (Sep 2020) is a lactulose 3-gas test (Trio Smart), which measures hydrogen sulfide, in addition to hydrogen and methane, offering the most comprehensive SIBO assessment.
Test Interpretation
Doctors and vary widely in how they interpret SIBO breath tests. What one physician calls negative, another calls positive. Labs also use differing criteria. There is no universally accepted standard at present, however a consensus of experts published their recommendations in 2017 (North American Breath Test Consensus). For explanation of various positive standards and interpretation with case examples, please see my article on test interpretation or either one of my SIBO courses.
Articles:
Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus.
SIBO: The Finer Points of Diagnosis, Test Interpretation, and Treatment by Drs Siebecker & Sandberg-Lewis
How to Interpret Hydrogen Breath Tests by Dr Ghoshal
Implementation and Interpretation of Hydrogen Breath Tests by Dr Eisenmann et al
Articles:
Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus.
SIBO: The Finer Points of Diagnosis, Test Interpretation, and Treatment by Drs Siebecker & Sandberg-Lewis
How to Interpret Hydrogen Breath Tests by Dr Ghoshal
Implementation and Interpretation of Hydrogen Breath Tests by Dr Eisenmann et al
Videos
From Dr Weinstock, SIBO clinician and researcher
Breath Test kit explanation & demo
Breath Test short video
Breath Test longer video
From Dr Pimentel, SIBO researcher, clinician and author of A New IBS Solution
IBS, Breath Test and SIBO, with demo
Breath Test kit explanation & demo
Breath Test short video
Breath Test longer video
From Dr Pimentel, SIBO researcher, clinician and author of A New IBS Solution
IBS, Breath Test and SIBO, with demo
Order a SIBO Breath Test Kit
For those without a prescription/doctor's order in the U.S., a 3-hour, 8-tube, lactulose breath test is available from: Direct Labs and True Health Labs. And a 2-hour 8-tube test is available from trio smart. When using trio smart, I recommend collecting breath every 22 minutes to stretch the test to 3-hours.
IBS Blood Test
Anti Vinculin & CDT B Antibodies
The IBS Blood test measures antibodies against the bacterial toxin Cytolethal Distending Toxin B (CdtB) and the small intestine nerve protein Vinculin. It detects SIBO that developed after bacterial food poisoning through an autoimmune process. Food poisoning is thought to be the most common cause of SIBO (& IBS) and is also known as travelers diarrhea and stomach flu. Two versions of this test have been correlated with the diarrhea and mixed type of SIBO.(1, 2) Constipation cases caused by food poisoning are also possible, but less likely.
Interpretation
- If the test is Positive (both antibodies): It means the migrating motor complex waves in the small intestine are deficient and can not clear bacteria out (= SIBO). It also rules out Inflammatory Bowel Disease with 98% probability (if using IBS Smart blood test specifically - see test Availability below). A SIBO breath test is then recommended to help choose treatment type and duration, which depend on gas type and amount (shown with a breath test - see below).
- If the test is Negative (both antibodies): A SIBO breath test is needed to complete the investigation of SIBO (see below). The breath test diagnoses SIBO from all causes, whereas the IBS Blood test only detects SIBO caused from food poisoning.
- If Vinculin alone is Positive: It means there is autoimmunity and the prognosis is longer/more complicated. Prokinetics to help stimulate the migrating motor complex are indicated.
- If Cdt B alone is Positive: If means there is no autoimmunity and the prognosis is shorter/more favorable.
Uses
1. A screening blood test for IBS / Diagnose SIBO (if positive)
- From food poisoning, but not other causes. Screening test because food poisoning is estimated to account for a majority of IBS/SIBO.
2. Differential diagnosis
- Rules out Inflammatory Bowel Disease with 98% probability (if positive & using IBS Smart blood test specifically)
- Avoids potentially unnecessary colonoscopy
3. Diagnose underlying cause and cause of SIBO if test is positive
- Deficient Migrating Motor Complex/Motility in the small intestine is the physiologic underlying cause of SIBO (if test is positive)
- Diagnoses Food Poisoning as the cause of SIBO/IBS (if test is positive)
Availability: from 4 labs
1. IBS Smart - Gemelli Biotech. Updated and improved version with greater specificity. (2nd generation)
2. IBSchek - Commonwealth Diagnostics International. Original version 2015 (1st generation)
3. Array 22 Irritable Bowel/SIBO Screen - Cyrex. Has additional markers.
4. IBSSure - Vibrant America
Interpretation
- If the test is Positive (both antibodies): It means the migrating motor complex waves in the small intestine are deficient and can not clear bacteria out (= SIBO). It also rules out Inflammatory Bowel Disease with 98% probability (if using IBS Smart blood test specifically - see test Availability below). A SIBO breath test is then recommended to help choose treatment type and duration, which depend on gas type and amount (shown with a breath test - see below).
- If the test is Negative (both antibodies): A SIBO breath test is needed to complete the investigation of SIBO (see below). The breath test diagnoses SIBO from all causes, whereas the IBS Blood test only detects SIBO caused from food poisoning.
- If Vinculin alone is Positive: It means there is autoimmunity and the prognosis is longer/more complicated. Prokinetics to help stimulate the migrating motor complex are indicated.
- If Cdt B alone is Positive: If means there is no autoimmunity and the prognosis is shorter/more favorable.
Uses
1. A screening blood test for IBS / Diagnose SIBO (if positive)
- From food poisoning, but not other causes. Screening test because food poisoning is estimated to account for a majority of IBS/SIBO.
2. Differential diagnosis
- Rules out Inflammatory Bowel Disease with 98% probability (if positive & using IBS Smart blood test specifically)
- Avoids potentially unnecessary colonoscopy
3. Diagnose underlying cause and cause of SIBO if test is positive
- Deficient Migrating Motor Complex/Motility in the small intestine is the physiologic underlying cause of SIBO (if test is positive)
- Diagnoses Food Poisoning as the cause of SIBO/IBS (if test is positive)
Availability: from 4 labs
1. IBS Smart - Gemelli Biotech. Updated and improved version with greater specificity. (2nd generation)
2. IBSchek - Commonwealth Diagnostics International. Original version 2015 (1st generation)
3. Array 22 Irritable Bowel/SIBO Screen - Cyrex. Has additional markers.
4. IBSSure - Vibrant America
Site author: Dr Allison Siebecker