title: Clinical evaluation, biochemistry and genetic polymorphism analysis for the diagnosis of lactose intolerance in a population from northeastern Brazil.
abstract: OBJECTIVE
  This work aimed to evaluate and correlate symptoms, biochemical blood test results and single nucleotide polymorphisms for lactose intolerance diagnosis.
  
  
  METHODS
  A cross-sectional study was conducted in Fortaleza, Ceará, Brazil, with a total of 119 patients, 54 of whom were lactose intolerant. Clinical evaluation and biochemical blood tests were conducted after lactose ingestion and blood samples were collected for genotyping evaluation. In particular, the single nucleotide polymorphisms C>T-13910 and G>A-22018 were analyzed by restriction fragment length polymorphism/polymerase chain reaction and validated by DNA sequencing.
  
  
  RESULTS
  Lactose-intolerant patients presented with more symptoms of flatulence (81.4%), bloating (68.5%), borborygmus (59.3%) and diarrhea (46.3%) compared with non-lactose-intolerant patients (p<0.05). We observed a significant association between the presence of the alleles T-13910 and A-22018 and the lactose-tolerant phenotype (p<0.05). After evaluation of the biochemical blood test results for lactose, we found that the most effective cutoff for glucose levels obtained for lactose malabsorbers was <15 mg/dL, presenting an area under the receiver operating characteristic curve greater than 80.3%, with satisfactory values for sensitivity and specificity.
  
  
  CONCLUSIONS
  These data corroborate the association of these single nucleotide polymorphisms (C>T-13910 and G>A-22018) with lactose tolerance in this population and suggest clinical management for patients with lactose intolerance that considers single nucleotide polymorphism detection and a change in the biochemical blood test cutoff from <25 mg/dL to <15 mg/dL.
authors.affiliation: Instituto de Biomedicina do Semi-Árido Brasileiro (IBISAB) & Departamento de Fisiologia e Farmacologia, Universidade Federal do Ceará, Fortaleza/, CE, Brazil.
authors.forename: Paulo Roberto Lins
authors.initials: PR
authors.lastname: Ponte
authors.affiliation: Instituto de Biomedicina do Semi-Árido Brasileiro (IBISAB) & Departamento de Fisiologia e Farmacologia, Universidade Federal do Ceará, Fortaleza/, CE, Brazil.
authors.forename: Pedro Henrique Quintela Soares
authors.initials: PH
authors.lastname: de Medeiros
authors.affiliation: Instituto de Biomedicina do Semi-Árido Brasileiro (IBISAB) & Departamento de Fisiologia e Farmacologia, Universidade Federal do Ceará, Fortaleza/, CE, Brazil.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Havt
authors.affiliation: Instituto de Biomedicina do Semi-Árido Brasileiro (IBISAB) & Departamento de Fisiologia e Farmacologia, Universidade Federal do Ceará, Fortaleza/, CE, Brazil.
authors.forename: Joselany Afio
authors.initials: JA
authors.lastname: Caetano
authors.affiliation: Instituto de Biomedicina do Semi-Árido Brasileiro (IBISAB) & Departamento de Fisiologia e Farmacologia, Universidade Federal do Ceará, Fortaleza/, CE, Brazil.
authors.forename: David A C
authors.initials: DA
authors.lastname: Cid
authors.affiliation: Instituto de Biomedicina do Semi-Árido Brasileiro (IBISAB) & Departamento de Fisiologia e Farmacologia, Universidade Federal do Ceará, Fortaleza/, CE, Brazil.
authors.forename: Mara de Moura Gondim
authors.initials: Mde M
authors.lastname: Prata
authors.affiliation: Instituto de Biomedicina do Semi-Árido Brasileiro (IBISAB) & Departamento de Fisiologia e Farmacologia, Universidade Federal do Ceará, Fortaleza/, CE, Brazil.
authors.forename: Alberto Melo
authors.initials: AM
authors.lastname: Soares
authors.affiliation: Instituto de Biomedicina do Semi-Árido Brasileiro (IBISAB) & Departamento de Fisiologia e Farmacologia, Universidade Federal do Ceará, Fortaleza/, CE, Brazil.
authors.forename: Richard L
authors.initials: RL
authors.lastname: Guerrant
authors.affiliation: Center for Global Health and Center for Public Health Genome, University of Virginia, Charlottesville, Virginia, US.
authors.forename: Josyf
authors.initials: J
authors.lastname: Mychaleckyj
authors.affiliation: Instituto de Biomedicina do Semi-Árido Brasileiro (IBISAB) & Departamento de Fisiologia e Farmacologia, Universidade Federal do Ceará, Fortaleza/, CE, Brazil.
authors.forename: Aldo Ângelo Moreira
authors.initials: AÂ
authors.lastname: Lima
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000483:Alleles; D019540:Area Under Curve; D001786:Blood Glucose / Q000032:analysis; D001938:Brazil / Q000208:ethnology; D003430:Cross-Sectional Studies; D005260:Female; D005838:Genotype; D006801:Humans; D007785:Lactose / Q000493:pharmacokinetics; D007787:Lactose Intolerance / Q000097:blood / Q000175:diagnosis* / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D012150:Polymorphism, Restriction Fragment Length; D020641:Polymorphism, Single Nucleotide; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D007785:Lactose