title: A comparison of diagnostic tests for lactose malabsorption--which one is the best?
abstract: BACKGROUND
  Perceived milk intolerance is a common complaint, and tests for lactose malabsorption (LM) are unreliable. This study assesses the agreement between diagnostic tests for LM and describes the diagnostic properties of the tests.
  
  
  METHODS
  Patients above 18 years of age with suspected LM were included. After oral intake of 25 g lactose, a combined test with measurement of serum glucose (s-glucose) and hydrogen (H2) and methane (CH4) in expired air was performed and symptoms were recorded. In patients with discrepancies between the results, the combined test was repeated and a gene test for lactose non-persistence was added. The diagnosis of LM was based on an evaluation of all tests. The following tests were compared: Increase in H2, CH4, H2+CH4 and H2+CH4x2 in expired air, increase in s-glucose, and symptoms. The agreement was calculated and the diagnostic properties described.
  
  
  RESULTS
  Sixty patients were included, seven (12%) had LM. The agreement (kappa-values) between the methods varied from 0.25 to 0.91. The best test was the lactose breath test with measurement of the increase in H2 + CH4x2 in expired air. With a cut-off level < 18 ppm, the area under the ROC-curve was 0.967 and sensitivity was 100%. This shows that measurement of CH4 in addition to H2 improves the diagnostic properties of the breath test.
  
  
  CONCLUSIONS
  The agreement between commonly used methods for the diagnosis of LM was unsatisfactory. A lactose breath test with measurement of H2 + CH4x2 in expired air had the best diagnostic properties.
authors.affiliation: Department of Medicine, Innlandet Hospital Trust, Gjøvik, Norway. oistein.hovde@sykehuset-innlandet.no
authors.forename: Øistein
authors.initials: Ø
authors.lastname: Hovde
authors.forename: Per G
authors.initials: PG
authors.lastname: Farup
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000378:metabolism*; D001944:Breath Tests / Q000379:methods; D002849:Chromatography, Gas / Q000379:methods; D003937:Diagnosis, Differential; D005260:Female; D005500:Follow-Up Studies; D005951:Glucose Tolerance Test; D006801:Humans; D007785:Lactose / Q000378:metabolism*; D007787:Lactose Intolerance / Q000097:blood / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D011795:Surveys and Questionnaires; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D007785:Lactose