title: Hydrogen breath testing versus LCT genotyping for the diagnosis of lactose intolerance: a matter of age?
abstract: BACKGROUND
  Two single nucleotide polymorphisms (-13910 C/T and -22018 G/A) upstream of the lactase gene (LCT) have been found to be associated with lactose tolerance in Europeans.
  
  
  METHODS
  In one hundred and twenty Austrian outpatients, who visited the physician's office for symptoms of irritable bowel syndrome (IBS), hydrogen breath testing (HBT) and LCT genotyping by polymerase chain reaction and reverse-hybridisation were performed in parallel.
  
  
  RESULTS
  The coincidence between a genotype suggesting lactase non-persistence (lactose intolerance) and a positive HBT result was almost perfect (97.4% for LCT-13910 C/T and 100% for LCT-22018 G/A). Between a genotype indicating lactase persistence (lactose tolerance) and a negative HBT result the coincidence was lower (72% and 71.4%, respectively). Among heterozygotes, there was a statistically significant increase in the proportion of positive HBT results with age. Both SNPs were in accordance in 117/120 (97.5%) patients.
  
  
  CONCLUSIONS
  Genetic analysis of LCT-13910 C/T and LCT-22018 G/A is a good indicator for the presence of lactose intolerance. Because age, as well as a number of secondary causes (e.g. celiac disease), can influence HBT results, it is useful to combine HBT and genetic analysis in the diagnostic assessment of IBS.
authors.affiliation: Department of Clinical Nutrition, Medical University of Innsbruck, Innrain 66a, A-6020 Innsbruck, Austria.
authors.forename: Michaela
authors.initials: M
authors.lastname: Kerber
authors.forename: Christian
authors.initials: C
authors.lastname: Oberkanins
authors.forename: Gernot
authors.initials: G
authors.lastname: Kriegshäuser
authors.forename: Barbara
authors.initials: B
authors.lastname: Kollerits
authors.forename: Astrid
authors.initials: A
authors.lastname: Dossenbach-Glaninger
authors.forename: Dietmar
authors.initials: D
authors.lastname: Fuchs
authors.forename: Maximilian
authors.initials: M
authors.lastname: Ledochowski
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001317:Austria; D001944:Breath Tests / Q000379:methods*; D002648:Child; D003951:Diagnostic Errors; D005260:Female; D005820:Genetic Testing / Q000379:methods / Q000592:standards*; D005838:Genotype; D006801:Humans; D006859:Hydrogen / Q000032:analysis*; D043322:Lactase / Q000235:genetics*; D007787:Lactose Intolerance / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide; D015203:Reproducibility of Results
chemical_list: D006859:Hydrogen; D043322:Lactase