Added Value of 13C Analysis in Breath Tests in H2-Negative Subjects to Diagnose Lactose Malabsorption: A Proof of Concept Study

Diagnosing lactose malabsorption is usually based on hydrogen excretion in breath after a lactose challenge. However, a proportion of subjects with lactose malabsorption will not present a rise in hydrogen. Measuring excretion of methane or stable isotope labeled 13CO2 after ingestion of 13C-lactose has been proposed to mitigate this problem. The aim of the study was to assess the performance of measuring methane and 13CO2 in individuals with normal hydrogen excretion compared to a genetic lactase non-persistence test. Individuals referred for lactose breath testing and healthy controls were included. Participants received 13C-enriched lactose, performed breath testing, and underwent genotyping for a marker of lactase non-persistence (13910C*T). Using genotype as gold standard, the performance of measuring methane and 13CO2 excretion was assessed. 151 subjects participated in the study, 50 of which presented a lactase non-persistent genotype. Of these, 72