Hydrogen breath testing (BT) is a useful non-invasive test for diagnosing small intestinal bacterial overgrowth (SIBO) and carbohydrate maldigestion. In a proportion of patients methane is produced at the expense of hydrogen leading to false negative results. This retrospective study evaluated the diagnostic yield of methane testing in addition to hydrogen.Methods
Electronic records were interrogated for the results of all glucose and lactose BT performed for SIBO and lactose intolerance respectively between 22/05/2015 and 03/01/2018 using the GastroCH4ECK® machine, Bedfont® Scientific Ltd.Results
During the study interval 569 patients (age range 16–86 y, 66% female) were referred for BT with glucose (48.5%) or lactose challenge (51.5%). Hydrogen and methane production was positive in 10.1% (71.4% female) and 4.7% (61.5% female) of patients undergoing glucose BT for SIBO. Two patients were hydrogen/methane co-producers. Hence 28.2% of patients with SIBO solely produced methane and would have been missed with only hydrogen assessment.Results
Hydrogen and methane production was positive in 25.6% (80.0% female) and 5.1% (68% female) of patients undergoing lactose BT for lactose malabsorption respectively. Two patients were hydrogen/methane co-producers. 14.8% of patients with positive lactose BT only produced methane and would have been missed with hydrogen mono-testing.Results
Overall 18.9% of all patients with a positive BT (n=24, 75% female) were sole methane-producers that would have been misdiagnosed if hydrogen mono-testing was conducted.Conclusions
In this study we have demonstrated that combined hydrogen/methane BT helps optimise diagnosis in patients with suspected SIBO or lactose intolerance. An extra 28.2% of positive breath tests for patients with SIBO and 14.8% for lactose malabsorption were identified with the addition of methane to hydrogen testing. Interestingly the proportion of patients producing methane was higher in SIBO than lactose malabsorption. Compared with the overall study population, a greater proportion of males tested positive for methane on glucose challenge. In comparison a greater proportion of females were methane positive on lactose BT. Currently only the minority of centres offer methane testing and our results suggest that a significant number of patients with possible SIBO or lactose malabsorption may be missed. Methane BT should be considered particularly for male patients with suspected SIBO.