Improved accuracy of lactose tolerance test in children, using expired H2 measurement.

Expired hydrogen and blood glucose were measured during an oral lactose tolerance test in 163 children aged between 9 months and 14 years. Lactose malabsorption, defined as an abnormal increase in expired H2 during a lactose tolerance test, was found in 54 children. Of these, 30 were found to be lactose intolerant as the increased expired H2 was accompanied by clinical symptoms. The other 109 children, in whom there was no rise in expired H2, were assumed to have normal lactose absorption. In children with lactose intolerance the increase in expired H2 tended to occur earlier after lactose ingestion than in children with malabsorption. The mean value of the rise in blood glucose was 2.4 mmol/100 ml) in the lactose-tolerant children and 1.0 mmol/1 (18 mg/100 ml) in the lactose-intolerant ones. Although this difference is significant (p less than 0.001), the rise in blood glucose, in predicting the correct diagnosis, was wrong in 13% of cases in the lactose-tolerant group, and wrong in 37% in the lactose-intolerant group (95% confidence limits 9-19% and 22-53% respectively). It is concluded that a rise in blood glucose, whether or not of more that 1.2 mmol/1 (22mg/100 ml) is of little help in differentiating lactose tolerance from intolerance.