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Confused about SIBO Test Protocol

Discussion in 'Diagnostic Guidelines and Laboratory Testing' started by Scotty81, Jan 30, 2015.

  1. Scotty81



    My daughter will be taking a breath test shortly to see if she has SIBO (small intestinal bacterial overgrowth). I'm looking for some expert medical advice regarding the protocol of what to eat two days prior to the test. Here's why.

    I understand that if one has SIBO, it means that one has bacteria in the small intestine, where it is not supposed to be. So, for the test, when one drinks a carbohydrate solution, a person will expel hydrogen as a result of the bacteria digesting the carbohydrates. It looks like this reaction won't happen, or will only happen on a much smaller scale, if one consumes only proteins and fats.

    The testing instructions from Metametrix says to eat primarily proteins and fats prior to the test, and to avoid certain carbohydrates (e.g. pastas) and sparingly limit other grains (e.g. rice). If you look at the instructions on various hospitals for the SIBO test (e.g. Brigham and Women's Hospital) , they essentially say that eating carbs prior to the test can produce a false positive. Interestingly enough, my daughter's practitioner recommended that she consume a regular diet and ignore the test directions. So, here are some brain teasers about all that!

    If one consumes carbs, then I could certainly see how one could get a false positive. My question is, if you consume carbs and do have SIBO, will the hydrogen or methane results be so positive that you don't have to worry about getting a false positive? Or, do you have to worry about getting an equivocal result which would lead you to think that you have SIBO when you really don't? I can see that even if you eat all the carbs you can, and you don't have bacteria in the small intestine, I would think that there wouldn't be any bacteria to produce that hydrogen gas in the first place.

    On the other side, what if you follow the strict preparation diet (e.g. mostly proteins and fats)? Is it possible that one could get a false negative with the results? I would imagine that since the lactulose solution that one drinks is a carbohydrate, then if one has SIBO, you should see it in the test results, whether you ate carbs for the prior two days or not.

    I can also see my daughter's practitioner's advice which is just to eat normally prior to the test. Thus, if your normal diet is producing hydrogen/methane gas from the bacteria, then that will show up on the baseline (which they have you measure prior to drinking any solution). And, the test will measure more of how your body normally reacts vs. what it might do if you are on a low carbohydrate diet.

    Still if the latter is true, then i wonder why all the fuss from the directions on both the test kit and the hospitals that offer this test that strongly say to avoid most carbs for accurate results. Although there is no perfect test out there, it's certainly confusing when one gets mixed signals as to testing protocol.

    Thanks in advance for anyone's sage wisdom regarding this testing protocol.

  2. PeterPositive

    PeterPositive Senior Member

    Small note: the small intestine does contain bacteria in healthy people too, around 10^4 CFU/ml... when the number grows you can have SIBO, and all the related issues. That's why probiotics are used as a therapy with or without antibiotics, depending on the case.

  3. AkeBono


    When i did my SIBO test two years ago
    i was adviced to eat "usual diet" the night before also BIT of carbs not sugars but not exagerating. I ate veggies for carbs. BUT I would follow their instructions for the test, maybe different technology is involved who knows.

    they told the main thing was the fasting period like 12 hours if I remember corectly and then the sugary stuff on empty stomach. Usually 12 hours are enough to clear the byproducts of bacteria, ...especially if you drink water. at least for me it was. The next day when i took the lactulose I was drunk in 5 minutes AND again in 45 minutes. My results was more on the methane side than hidrogen.i usually have constipation.
    If youd like to compare info here is the lab info about test:

    Im not 100% sure but some tests include also a part with manitol or something like that besides lactulose. dont remember clearly. anyway some labs test two substances apparently. good luck!
    Sherlock likes this.

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