SIBO Diagnosis

Lactulose Breath Test

This is currently the best test for SIBO. It measures methane and hydrogen levels over the course of three hours.

Lactulose breath tests are available from many doctors and laboratories.

Important things to know:

• Make sure the test measures BOTH methane and hydrogen; many older testing centers just look at hydrogen.
• Lactulose is the test you want, not glucose (higher incidence of false negatives).
• The three-hour (vs. two-hour) test is preferred.
• Lactulose is not the same as lactose... be careful not to order the wrong test.
• Adherence to the prep diet is very important, and I'd probably skip the rice just to be safe.
• A negative test still doesn't rule out fungal overgrowth (SIFO) or hydrogen sulfide SIBO.
• A positive test doesn't mean that there aren't other GI issues going on as well, such as IBD or celiac disease.
• This test is more accurate, less expensive, and less invasive than an endoscopy aspirate culture, but an endoscopy culture can provide more detail sometimes by identifying specific microorganisms, funguses, etc.
• To learn how to interpret your test, this article is a good place to start. And here is the establishment consensus as of 2017.

Example test output:

Utility of SIBO lactulose breath test for methane and hydrogen:

• Establishes SIBO diagnosis (does not rule out other concurrent conditions).
• Guides treatment - methane-predominant and hydrogen-predominant SIBO require different treatments.
• Indicates severity of case, which has implications for treatment length and prokinetic use (more severe cases are more likely to be chronic and require an ongoing prokinetic).
  • >50ppm of either gas is starting to get bad and could take 2+ rounds of antibiotics to eradicate.
  • >100ppm of either gas is really bad and could take 4+ rounds of antibiotics to eradicate.

Food poisoning / IBS blood test

Not as valuable for constipation-predominant SIBO.

This test looks for food-poisoning-related antibodies in the blood. If these antibodies are present, you know the root cause of your SIBO is semi-permanent intestinal nerve damage from food poisoning, and you can treat the underlying cause appropriately with prokinetics, meal spacing, and (to a lesser extent) nerve healers.

The higher the anti-vinculin value, the more likely your case will be chronic and difficult to treat (anti-vinculin > 3.0 starts to be really challenging to treat). Similarly, a positive test result means you'll want to be extra careful not to get food poisoning again at the risk of worsening your SIBO symptoms and outlook.

Knowing the underlying cause of a condition like SIBO is helpful not only for guiding treatment but is often also a relief to those that have been grasping at straws for a long time trying to understand what is wrong with them.

Other underlying causes

There are many, many underlying or predisposing conditions that can cause SIBO. As mentioned elsewhere, food poisoning appears to be the most common and can be tested with the IBS Blood Test described above. That would be a good place to start after a positive breath test for diarrhea or mixed-type SIBO patients.

Other tests to possibly look at include small intestine motility studies and a barium swallow to look for obstructions, adhesions, and any other structural issues in the small intestines. For motility testing, you're generally trying to see if the migrating motor complex in the small intestine is functioning properly. "Smart pills" at places like the University of Louisville can measure this remotely. Otherwise the main test is a procedure called antroduodenal manometry.

Another easy one to check off the list would be Ehlers-Danlos syndrome. More underlying causes to consider are hypothyroid, diabetes, autoimmune issues, and the list goes on and on. SIBO is almost always a consequence of something else.

This list is not exhaustive, but don't be discouraged -- treatment of the underlying cause is often the same. A majority of SIBO ultimately occurs because of poor gastrointestinal motility, and there is a class of drugs called prokinetics that are specifically designed to treat gut motility issues. We'll dive into prokinetics more in the treatment section.

Because SIBO symptoms overlap with many other diseases (such as IBD), it is not possible to diagnose SIBO by symptoms alone. However, given the prevalence of SIBO, we can strengthen our hypothesis with a few clues:

Common symptoms:

• Bloating
• Diarrhea
• Constipation
• Abdominal Pain
• Acid Reflux
• (many more)

Made worse by:

• Higher carb intake
• Fiber / complex carbs / whole grains / pre-biotics
• Lactose

Made better by:

• Low-carb / low-fiber diet (or a SIBO diet)
• Fasting
• Antibiotics

History:

• IBS - Irritable Bowel Syndrome
• Food poisoning
• Use of PPI's (proton pump inhibitors)
• Opioid drug use
• Abdominal surgery
• Rosacea
• Autoimmune disease
• Diabetes
• Restless Leg Syndrome
• Brain trauma
• And more