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.9,11

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).12 False-negative results occur much less than false-negative results observed using the blood test,2,3,5 reportedly ranging from 5-18% of all lactose malabsorbers.4,6,7,10 Most false-negative tests can be avoided by testing for methane,1 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.


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  2. Davidson, P.; Robb, T.A. Value of breath hydrogen analysis in management of diarrheal illness in childhood: Comparison with duodenal biopsy. J. Ped Gastroenterol Nutr 1985 (Jun); 4(3):381-7
  3. DiPalma,A.; Narvaez, R.M. Prediction of lactose malabsorption in referral patients. Dig Dis Sci 1988 (Mar);33:303-7
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  6. Filali, A, Ben Hassine, L, Dhouib, H, Matri, S, Ben Ammar, A and Garoui, Study of malabsorption of lactose by the hydrogen breath test in a population of 70 Tunisian adults. Gastroenterol Clin Biol. 1987 (Aug);11(8-9):554-7
  7. Hammer, F.; Petritsch, W.; Pristautz, H.; Krejs, G.J. Assessment of the influence of hydrogen nonexcretion on the usefulness of the hydrogen breath test and lactose tolerance Wien Klin Wochenschr 1996;108(5):137-41
  8. Newcomer, D; McGill, D.B.; Thomas, R.J.; Hofmann, A.F. Prospective comparison of indirect methods for detecting lactase deficiency. New Engl J Med. 1975; 293:1232-6
  9. Pimentel An evidence-based treatment algorithm for IBS based on a bacterial/SIBO hypothesis: Part 2. Am J Gastroenterol. 2010 Jun;105(6):1227-30. PMID: 20523308
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  11. Siebecker A, Sandberg-Lewis The Finer Points of Diagnosis, Test Interpretation, and Treatment, Naturopathic Doctor National Review, January 2014, 10:46.
  12. Solomons, W. Evaluation of carbohydrate absorption: The hydrogen breath test in clinical practice. Clin Nutr J. 1984; 3:71-78