Objective: The objective of the submitted paper was to report experience with the diagnosis of lactose intolerance by analysis of the hydrogen concentration in expired air and to draw attention to contemporary therapeutic possibilities of this condition. Method: The authors made a retrospective analysis of patients examined on account of suspected lactose intolerance by assessing the hydrogen concentration in the expired air using an apparatus of the Dutch Co. Elphymed Lactoscreen H2 Breath Tester between January 1995 till December 1998. Results: During the mentioned period the authors used this test in 429 (59.75%) of 718 examined children aged 3 months to 18 years with lactose intolerance. An elevated hydrogen concentration was found in 87 of 216 children (40.3%) under 3 years and in 342 of 502 children (68.1%) of children above 3 years. Congenital alactasia was not detected in any of the patients, transitory secondary hypolactasia was diagnosed in all 87 children under 3 years and also in 36.2% children (126 of 342) above 3 years with pathological results of the initial test. In almost two thirds of patients above three years (in 216 of 342 children 63.16%) with a mean age of 11.5 years (4.5 to 17 years) who were examined on account of relapsing abdominal pain frequently associated with meteorism, increased flatulence and intermittent loose stools resp. the authors diagnosed primary genetic hypolactasia caused by persisting pathological hydrogen concentrations without clinical symptoms after a dietary regime administered for several months. Conclusion: From the results ensues that lactose intolerance is a frequent disease which can be diagnosed also by a non-invasive test, and based on the latter, the clinical course of the disease can be influenced by lactose-free or low-lactose formulas in younger children and yoghurt with a probiotic culture in older children.

        Key words: lactose – hypolactasia – hydrogen concentration in the expired air – diet