Additional Value of CH(4) Measurement in a Combined (13)C/H(2) Lactose Malabsorption Breath Test: A Retrospective Analysis

The lactose hydrogen breath test is a commonly used, non-invasive method for the detection of lactose malabsorption and is based on an abnormal increase in breath hydrogen (H(2)) excretion after an oral dose of lactose. We use a combined (13)C/H(2) lactose breath test that measures breath (13)CO(2) as a measure of lactose digestion in addition to H(2) and that has a better sensitivity and specificity than the standard test. The present retrospective study evaluated the results of 1051 (13)C/H(2) lactose breath tests to assess the impact on the diagnostic accuracy of measuring breath CH(4) in addition to H(2) and (13)CO(2). Based on the (13)C/H(2) breath test, 314 patients were diagnosed with lactase deficiency, 138 with lactose malabsorption or small bowel bacterial overgrowth (SIBO), and 599 with normal lactose digestion. Additional measurement of CH(4) further improved the accuracy of the test as 16% subjects with normal lactose digestion and no H(2)-excretion were found to excrete CH(4). These subjects should have been classified as subjects with lactose malabsorption or SIBO. In conclusion, measuring CH(4)-concentrations has an added value to the (13)C/H(2) breath test to identify methanogenic subjects with lactose malabsorption or SIBO.