What Causes A High Baseline Sample In A SIBO Test?


Welcome to my blog entitled ‘What Causes A High Baseline Sample In A SIBO Test?’.

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What Causes A High Baseline Sample In A SIBO Test??

Baseline elevations of expired hydrogen or methane seen in breath testing may be due to the oral microbiota, including methanogens. Variations in gas production such as those seen in this study has significant implications on test interpretation and subsequently on diagnosis.

This is the conclusion of a recent (2021) paper (1) that discusses how our oral microbiome may cause an elevated base line sample in SIBO breath tests which may lead to false negative results.

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The relationship between oral dysbiosis and gastrointestinal symptoms is under-explored. The prospect that identification and treatment of the oral microbiota may alter patient outcomes is an interesting possibility that warrants investigation.

This study suggests that the oral microbiota contributes to measurements of breath gases. In up to 30% of patients with at least one basal gas ≥ 10 ppm this may alter test outcomes and diagnosis, and therefore treatment. The relationship between oral bacterial overgrowth and functional gastrointestinal disorders beyond GI cancers and ulcers requires a thorough examination.

What mouthwash was used?

All subjects with ≥ 10 ppm of hydrogen or methane at baseline were administered a mouthwash using 10 mL of a chlorhexidine (1.2 mg/mL) mouthwash (Colgate Savacol) with instructions to move the mouthwash around the mouth for 20–30 s, forcing it between teeth and gargling before spitting it out and rinsing the mouth with water.

So a basic mouthwash would suffice (as long as it has chlorhexidine in it) : click here.


So what’s the take away? Well the authors suggest that until further data are available, it is recommended that the collection of two baseline samples when conducting breath testing—one before, and one after a mouthwash.

They explain that this practice will determine the likely contribution of oral microbiota in subsequent breath gas measurements and has the potential to add valuable information to the clinical dataset for patients.


  1. Hydrogen–methane breath testing results influenced by oral hygiene (click here)
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