Methane Gas in Breath Test is Associated with Non-Alcoholic Fatty Liver Disease.

Although the association between Body Mass Index (BMI) level and metabolic diseases as well as the association between the breath test results and BMI level have been studied, their relationship between breath hydrogen/methane level and metabolic diseases need to be further clarified. This study aimed to investigate how the composition of exhaled breath gases relates to metabolic disorders and their key risk factors. An elevated BMI level significantly increases the risk of developing metabolic disease; it was included in this study to find their association. Diabetes mellitus, dyslipidemia, hypertension, and non-alcoholic fatty liver disease (NAFLD) are metabolic diseases included in this study.&#xD;An analysis was performed on the medical records including the lactulose breath test (LBT) data of patients who visited the Ajou University Medical Center, Suwon, Republic of Korea, between January 2016 and December 2021. Subjects were grouped according to four different criteria of the LBT hydrogen and methane level: 1) Normal (N) (Hydrogen < 20 ppm and Methane < 3 ppm); 2) Hydrogen only (H+) (Hydrogen ≥ 20 ppm and Methane < 3 ppm); 3) Methane positive (M+) (Hydrogen < 20 ppm and Methane ≥ 3 ppm); and 4) Methane and hydrogen positive (M+/H+) (Hydrogen ≥ 20 ppm and Methane ≥ 3 ppm). Of 441 subjects, 325 (72.1%) had positive results for methane only (M+). BMI and prevalence of NAFLD were higher in subjects with M+ than in subjects with hydrogen and methane positivity (H+/M+). According to multivariate analysis, the odds ratio (OR) of M+ was 2.002 (with 95% CI: 1.244-3.221, P = 0.004) for NAFLD. Our results demonstrate that breath methane positivity is related to NAFLD and suggest that increased methane gas in breath tests has the potential to be an easily measurable biomarker for the diagnosis of NAFLD. &#xD.