Influencing Factors on Lactulose Breath Test Results

Background/Aims: This study aimed to identify the demographic and clinical factors associated with positive breath-test results and to assess the relationship between hydrogen and methane production in patients with suspected irritable bowel syndrome (IBS). Methods: The demographic and clinical factors of 268 patients with suspected IBS, who had undergone a lactulose breath test, were analyzed. Results: Of 268 patients included in this study, 143 (53.4%) were females. The median age and BMI of the patients was 58.0 years (range, 18.0-80.0 years) and 22.5 kg/m(2) (range, 14.4-34.3 kg/m(2)), respectively. A weak positive correlation was observed between the BMI and baseline hydrogen level (rho=0.134, p=0.031). Women were significantly more likely to show a >/=20 ppm increase in hydrogen within 90 min (early hydrogen increase, p=0.049), a >/=10 ppm increase in methane within 90 min (early methane increase, p=0.001), and a >/=10 ppm increase in methane between 90 min and 180 min (late methane increase, p=0.002) compared to men. The baseline hydrogen level was related to the baseline methane level (rho=0.592, p<0.001) and the maximal hydrogen level within 90 min was related to maximal methane level within 90 min (rho=0.721, p<0.001). Patients with an early hydrogen increase (43.8%) were more likely to show a positive result for an early methane increase compared to patients without an early increase in hydrogen (0%, p<0.001). Conclusions: Women were associated with high rates of positive lactulose breath-test results. In addition, methane production was correlated with hydrogen production.