[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 (range, 14.4-34.3 kg/m), 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.