title: Lactose intolerance: lactose tolerance test versus genotyping.
abstract: OBJECTIVE
  Adult lactose intolerance, which affects the majority of the population in the world, has been associated with a single nucleotide polymorphism, C-13910T, located upstream of the lactase gene.
  
  
  METHODS
  Adult patients undergoing lactose tolerance tests with lactose challenge and plasma glucose measurements were included in the study comprising 44 Swedes and 7 non-Swedish individuals. A real-time PCR method was established for the genotyping.
  
  
  RESULTS
  Out of 51 patients 48 had concordant results on genotyping and lactose tolerance tests, e.g. -13910T/T and -13910C/T genotypes had high glucose elevations. All patients with the heterozygous genotype, -13910C/T, had high glucose elevations, and no gene-dose relationship was observed when comparing maximal glucose increases for cases with -13910C/T and -13910T/T genotypes.
  
  
  CONCLUSIONS
  Genotyping could replace lactose challenge as a first-stage screening test in adults of European descent, but should be used together with tolerance tests in children and patients where secondary lactose intolerance is suspected.
authors.affiliation: Department of Medical Sciences, Clinical Chemistry, University Hospital, Uppsala, Sweden. peter.ridefelt@medsci.uu.se
authors.forename: Peter
authors.initials: P
authors.lastname: Ridefelt
authors.forename: Lena D
authors.initials: LD
authors.lastname: Håkansson
mesh_terms: D000328:Adult; D000368:Aged; D001483:Base Sequence; D016022:Case-Control Studies; D005260:Female; D005821:Genetic Techniques; D005838:Genotype; D005962:Glucosylceramidase / Q000032:analysis / Q000235:genetics*; D006801:Humans; D007787:Lactose Intolerance / Q000175:diagnosis* / Q000208:ethnology* / Q000235:genetics; D007789:Lactose Tolerance Test / Q000379:methods*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D011446:Prospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity; D013548:Sweden / Q000453:epidemiology
chemical_list: D005962:Glucosylceramidase