False Positive Results for SIBO Hydrogen Breath Test

Many practitioners share the misguided belief that a 90 minute or longer lactulose hydrogen breath test will provide a measure of distal small intestinal bacterial overgrowth (SIBO).  This is an inappropriate use of the test.  In most cases a rapid oro-caecal transit time has been misinterpreted as distal SIBO. This point was demonstrated in a 25 person study with IBS patients. The study used serial measurements of breath hydrogen and oro-caecal scintigraphy following ingestion of a test meal containing lactulose and ^99mTc.  The result was that ^99mTc had already reached the caecum in 88% of the patients before the hydrogen breath levels reached the threshold for a positive result for SIBO.  In conclusion the hydrogen breath test for SIBO will produce a large number of false positive results when testing beyond 60 minutes and is not reliable for detecting distal SIBO.

Ref: GUT 2011 Mar (334-40)