title: Lactase Non-Persistence Genotyping: Comparison of Two Real-Time PCR Assays and Assessment of Concomitant Fructose/Sorbitol Malabsorption Rates.
abstract: BACKGROUND
  Genetic testing is a standard technique for the diagnosis of primary adult-type hypolactasia, also referred to as lactase non-persistence. The aim of this study was to compare the lactase gene (LCT) C/T-13910 polymorphism genotyping results of two commercially available real-time (RT)-PCR assays in patients referred to our outpatient clinic for primary lactose malabsorption testing. Furthermore, concomitant conditions of fructose/sorbitol malabsorption were assessed.
  
  
  METHODS
  Samples obtained from 100 patients were tested in parallel using the LCT T-13910C ToolSet for Light Cycler (Roche, Rotkreuz, Switzerland) and the LCT-13910C>T RealFast Assay (ViennaLab Diagnostics GmbH, Vienna, Austria). Additionally, patients were also screened for the presence of fructose/sorbitol malabsorption by functional hydrogen (H2)/methane (CH4) breath testing (HMBT). Cohen's Kappa (κ) was used to calculate the agreement between the two genotyping methods. The exact Chi-Square test was performed to compare fructose/sorbitol HMBT with LCT genotyping results.
  
  
  RESULTS
  Twenty-one (21.0%) patients had a LCT C/C-13910 genotype suggestive of lactase non-persistence, and 79 (79.0%) patients were identified with either a LCT T/C-13910 or T/T-13910 genotype (i.e., lactase persistence). In all genotype groups, concordance between the two RT-PCR assays was 100%. Cohen's κ demonstrated perfect observed agreement (p < 0.001, κ = 1). Fructose and sorbitol malabsorption was observed in 13/100 (13.0%) and 25/100 (25.0%) individuals, respectively.
  
  
  CONCLUSIONS
  Both RT-PCR assays are robust and reliable LCT genotyping tools in a routine clinical setting. Concomitant fructose and/or sorbitol malabsorption should be considered in individuals with suspected lactase-non-persistence. However, standardization of clinical interpretation of laboratory HMBT results is required.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Enko
authors.forename: Verena
authors.initials: V
authors.lastname: Pollheimer
authors.forename: Stefan
authors.initials: S
authors.lastname: Németh
authors.forename: Helene
authors.initials: H
authors.lastname: Pühringer
authors.forename: Robert
authors.initials: R
authors.lastname: Stolba
authors.forename: Gabriele
authors.initials: G
authors.lastname: Halwachs-Baumann
authors.forename: Gernot
authors.initials: G
authors.lastname: Kriegshäuser
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001944:Breath Tests; D005260:Female; D005632:Fructose / Q000493:pharmacokinetics*; D005838:Genotype; D006801:Humans; D043322:Lactase / Q000172:deficiency* / Q000235:genetics*; D007787:Lactose Intolerance / Q000175:diagnosis*; D008297:Male; D008697:Methane / Q000378:metabolism; D008875:Middle Aged; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods*; D013012:Sorbitol / Q000493:pharmacokinetics*
chemical_list: D005632:Fructose; D013012:Sorbitol; D043322:Lactase; D008697:Methane