Lactose intolerance, detected by the hydrogen breath test, in infants and children with chronic diarrhoea.

Twenty-three infants and children aged 2½ months to 13 years with chronic diarrhoea and 6 patients without diarrhoea were investigated for lactose malabsorption with the hydrogen breath test (HBT) adapted for use in young infants and children. A further 8 children with proven or suspected coeliac disease were also investigated. The HBT was compared with the histology of the jejunal mucosa, mucosal lactase estimations, a lactose tolerance test, symptoms during the test, and follow-up after starting a lactose free diet. The 6 patients without diarrhoea showed no evidence of hypolactasia and the hydrogen (H)* concentration on the HBT was below 7 parts per million (ppm), a level considered to be clinically nonsignificant. 12 of the 23 patients with diarrhoea had a breath H concentration greater than 24 ppm and this correlated well with their clinical symptoms during or after the test and with the remission of the diarrhoea after lactose withdrawal. Of the remaining 11 patients with diarrhoea whose breath H concentration was lower than 25 ppm, symptoms did not improve when a lactose-free diet was started in 3, while a further 4 improved on a full diet. There was poor correlation between the HBT and the findings on the jejunal mucosal specimens. All but one of the coeliac patients had an HBT less than 20 ppm and none of these required lactose withdrawal for remission of symptoms. The HBT is a noninvasive test particularly suitable for outpatients and it gives a useful prognostic guide to the efficacy of lactose-free diet in the treatment of chronic diarrhoea in children.