Interpreting Results

There is no universal standard for interpreting breath test results. The NUNM SIBO Lab bases our reports on the manufacturer’s guidelines for reporting whether or not SIBO is suspected. These guidelines should be used to assist providers in further interpreting the results based on their clinical expertise.

The NUNM SIBO Lab’s standard interpretation of results for SIBO uses the difference between the peak level compared to the lowest previous level in the first 120 minutes (+/- 5 min deviation). If the resulting value is an increase greater than 20 PPM for H2, or greater than 12 PPM for CH4 – SIBO is suspected. In addition, SIBO is suspected if the increase in the combined hydrogen and methane gas value is greater than 15ppm over the lowest preceding value. At the NUNM SIBO center, we have also used an absolute value (rather than an increase) of 20 PPM (H2) or 12 PPM (CH4) to indicate SIBO. Also note that methane values may not increase, the baseline and all levels often remain high for the whole test.

False-positive results are rare, and are usually caused by not following the test preparation and collection guidelines (for example, smoking, sleeping or eating during the test or one hour before the test). False-negative results occur much less than false-negative results observed using the blood test, reportedly ranging from 5-18% of all lactose malabsorbers. Most false-negative tests can be avoided by testing for methane, but there are other situations that may cause false-negative results. For example, one or more invalid samples may lead to a false negative result. Please refer to this document which explains the most common errors that lead to invalid samples.

How does the analysis work?

The breath-tracker machine is manufactured by Quintron, and it works by checking the breath sample for an appropriate amount of carbon dioxide as well as the hydrogen and methane present. If the sample does not have enough carbon dioxide, it will consider it invalid and not give results for the other two gasses. If a test has an invalid sample, but is otherwise positive, the results are sent normally. If a test has an invalid sample, but is otherwise negative, the SIBO lab will send a notice to the provider that the results may be a false negative and recollection is warranted to obtain accurate results. Only in the situation of a possible false negative can the patient do a retest for the material cost only.

The results came back as a “possible false negative.” What does that mean?

Usually, this means that the air in the tube is not from the patient’s lungs, so it cannot give an accurate result. The tubes are vacuum sealed and when the rubber stopper is punctured, they will draw in the first air available, so it is important that the sample is truly air from the lungs. Please see the Invalid Samples Explanation for a more detailed explanation of how invalid samples occur and the ways to fix them.

The patient had a “possible false negative” test with an invalid sample. How do they retest?

We will send results to the ordering provider, who must confer with the patient to determine whether they want to retest. If so, the patient needs to contact the SIBO Lab within 30 days of the original test results being sent to the doctor.

The results say that this patient is positive. What now?

The NUNM SIBO Lab is only able to run the test and send results to the physician. We cannot give any medical advice for treatment of SIBO or any other illness. Treatment for SIBO can be a variety of things, from antibiotics, to herbal supplements, to the elemental diet, all depending on what you and your patient choose as the best course of action.

The results say that this patient is negative. What now?

We are a reference lab, so we base our “normal” and “high” on what the manufacturer (Quintron) has stated. According to them, a test is considered positive when the Hydrogen increases by 20ppm, the Methane by 12ppm, or the combined by 15ppm. Only when the results show a change greater than these numbers will it show as positive on the final test report.

Some doctors not only look at the change, but at the raw number itself. So a Hydrogen level over 20ppm, a Methane over 12ppm, or a combination over 15ppm would be positive to them. See this NDNR article by Allison Siebecker and Steven Sandberg-Lewis for examples and explanations of this.

Some doctors also feel that a Methane level of over 3 (regardless of increase levels) indicates a positive as there is some sort of bacteria present. (The only way you have methane in your system is from bacteria fermenting food). So the doctors who see that as a positive will treat it, even though the test itself says “negative” on the results. Visit this site for more information about negative results.

While not common, the possibility of a flat-line test has been documented in literature about SIBO with indications that up to 5% of test takers can have flat-line results, either indicating a negative SIBO test, or the presence of Hydrogen Sulfide (which the lactulose breath test does not check for).  See the links below for more information about H2S and flat-line SIBO tests:

Flatline SIBO Breath Test Results

The well balanced FODMAPer Blog

Diagnosis of SIBO

Microbial pathways in colonic sulfur metabolism