title: Diagnosing lactose malabsorption in children: difficulties in interpreting hydrogen breath test results.
abstract: Lactose malabsorption (LM) is caused by insufficient enzymatic degradation of the disaccharide by intestinal lactase. Although hydrogen (H2) breath tests (HBTs) are routinely applied to diagnose LM, false-negative results are not uncommon. Thirty-two pediatric patients (19 females, 13 males) were included in this prospective study. After oral lactose administration (1 g kg(-1) bodyweight to a maximum of 25 g), breath H2 was measured by electrochemical detection. HBT was considered positive if H2 concentration exceeded an increase of  ⩾20 ppm from baseline. In addition to H2, exhaled methane (CH4), blood glucose concentrations and clinical symptoms (flatulence, abdominal pain, diarrhea) were monitored. A positive HBT indicating LM was found in 12/32 (37.5%) patients. Only five (41.7%, 5/12) of these had clinical symptoms during HBT indicating lactose intolerance (LI). Decreased blood glucose concentration increments (⩽20 mg dL(-1) (⩽1.1 mmol L(-1))) were found in 3/5 of these patients. CH4 concentrations  ⩾10 ppm at any time during the test were observed in 5/32 (15.6%) patients and in 9/32 (28.1%) between 1 ppm and 9 ppm above baseline after lactose ingestion. In patients with positive HBT 10/12 (83.3%) showed elevated CH4 (>1 ppm) above baseline in breath gas, whereas in patients with negative HBT this figure was only 4/17 (23.5%). In addition to determining H2 in exhaled air, documentation of clinical symptoms, measurement of blood glucose and breath CH4 concentrations may be helpful in deciding whether in a given case an HBT correctly identifies patients with clinically relevant LM.
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Medical University of Innsbruck, Anichstrasse 35, 6020 Innsbruck, Austria. Breath Research Institute, University of Innsbruck, Rathausplatz 4, 6850, Dornbirn, Austria.
authors.forename: Veronika
authors.initials: V
authors.lastname: Ruzsanyi
authors.forename: Peter
authors.initials: P
authors.lastname: Heinz-Erian
authors.forename: Andreas
authors.initials: A
authors.lastname: Entenmann
authors.forename: Daniela
authors.initials: D
authors.lastname: Karall
authors.forename: Thomas
authors.initials: T
authors.lastname: Müller
authors.forename: Alexander
authors.initials: A
authors.lastname: Schimkowitsch
authors.forename: Anton
authors.initials: A
authors.lastname: Amann
authors.forename: Sabine
authors.initials: S
authors.lastname: Scholl-Bürgi
mesh_terms: D000284:Administration, Oral; D000293:Adolescent; D001786:Blood Glucose / Q000032:analysis; D001826:Body Fluids / Q000378:metabolism; D001944:Breath Tests / Q000379:methods*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D006859:Hydrogen / Q000032:analysis*; D007785:Lactose; D007787:Lactose Intolerance / Q000175:diagnosis*; D008297:Male; D008697:Methane / Q000032:analysis; D011446:Prospective Studies
chemical_list: D001786:Blood Glucose; D006859:Hydrogen; D007785:Lactose; D008697:Methane