Real-world Study of Three-gas Breath Testing Nationwide and the Association With Symptoms

Goals and Background: Hydrogen (H 2 ) breath testing (BT) is used to diagnose small intestinal bacterial overgrowth (SIBO), and methane (CH 4 ) to diagnose constipation. Recently, a third microbially derived gas, hydrogen sulfide (H 2 S), was added to BT and associated with diarrhea. Here, we assess a 3-gas BT nationwide, comparing the results to gastrointestinal (GI) symptoms. Study: Consecutive subjects (N=6000) undergoing 3-gas at-home BT were asked to complete a symptom questionnaire. Substrate choice (glucose or lactulose) was at physician’s discretion. H 2 , CH 4, and H 2 S levels, and presence/absence of SIBO (≥20 ppm rise in H 2 within 90 min), intestinal methanogen overgrowth (IMO) (≥10 ppm CH 4 ), and intestinal sulfide overproduction (ISO, defined here as ≥2 ppm H 2 S) were compared with symptom severity. Gas interactions and symptoms’ correlations were determined using machine learning (Uniform Manifold Approximation and Projection UMAP). Results: A total of 3004 subjects who completed breath tests and primary questions were included. Bloating was the most common reason for BT. More subjects reported severe or very severe symptoms for bloating (52.9%) than diarrhea (17.8%), constipation (17.1%), or abdominal pain (17.1%). SIBO positivity was more common using lactulose (27%) versus glucose (7.3%). Higher H 2 levels correlated with more severe diarrhea ( P =0.031), and CH 4 levels correlated with constipation ( P =0.002). Higher H 2 S levels correlated with more severe diarrhea ( P <0.0001), urgency ( P =0.003), and abdominal pain ( P =0.01). UMAP revealed that H 2 S levels increased symptom severity, and ISO (alone or with SIBO/IMO) drove greater diarrhea, urgency, bloating, and overall severity, with highest pain and severity in ISO alone. Conclusions: H 2 , CH 4 , and H 2 S are associated with unique symptoms: CH 4 with constipation and H 2 S with diarrhea and a greater overall symptom severity. Glucose appears less sensitive than lactulose, suggesting it could potentially miss some symptomatic patients.