Hydrogen and Methane Breath Test in the Diagnosis of Lactose Intolerance.

The hydrogen (H) breath test is a non-invasive investigation used to diagnose lactose intolerance (LI). Patients with LI may also expire increased amounts of methane (CH) during a lactose test. The aim of this study is to evaluate the contribution of CH measurements. We tested 209 children (1-17 years old) with symptoms suggesting LI with lactose H and CH breath tests. The result was positive when the H excretion exceeded 20 parts per million (ppm) and the CH was 10 ppm above the baseline. A clinician, blinded for the results of the breath test, registered the symptoms. Of the patient population, 101/209 (48%) were negative for both H and CH; 96/209 (46%) had a positive H breath test result; 31/96 (32%) were also positive for CH; 12/209 (6%) patients were only positive for CH. The majority of hydrogen producers showed symptoms, whereas this was only the case in half of the H-negative CH producers. Almost all patients treated with a lactose-poor diet reported significant symptom improvement. These results indicate that CH measurements may possibly be of additional value for the diagnosis of LI, since 5.7% of patients were negative for H and positive for CH, and half of them experienced symptoms during the test.