title: Validity and reliability of the 13C-methionine breath test for the detection of moderate hyperhomocysteinemia in Mexican adults.
abstract: BACKGROUND
  Hyperhomocysteinemia (Hhcy) is considered an independent risk factor for vascular diseases and, more recently, for dementia. The methionine loading test (MLT) is useful for diagnosing additional subjects with moderate Hhcy. However, it is a complex and time-consuming procedure. A noninvasive test for the diagnosis of moderate Hhcy is desirable.
  
  
  METHODS
  The study protocol consisted of three consecutive visits. During the first visit, we performed an MLT to characterize the Hhcy status of 75 healthy adult subjects. For the breath test protocol, we selected a subsample and assigned to the control group 17 subjects with fasting and post-loading homocysteine (Hcy) ≤12 and <42.3 μmol/L, respectively, and to the Hhcy group 16 subjects with fasting Hcy ≤12 and >42.3 μmol/L after loading. Selected subjects were requested to have a second visit to perform a breath test within 1-4 weeks following the MLT test and received an oral dose of 2.5 mg/kg of 1-13C-methionine dissolved in water. Breath samples were collected at basal, 20, 40, 60, 80, 100 and 120 min (test 1). The same procedure was repeated within 1 week (test 2).
  
  
  RESULTS
  MLT was useful for diagnosing almost twice the number of individuals with Hhcy (24%) in comparison with the fasting determination alone (13.3%). The 13C-methionine breath test reported a sensitivity of 81.3% and a specificity of 64.7% against the MLT. The coefficient of variation between breath test 1 and breath test 2 was 9.0±5.4%.
  
  
  CONCLUSIONS
  The 13C-methionine breath test is a valid and reliable method for identifying subjects with moderate Hhcy.
authors.forename: Jorge
authors.initials: J
authors.lastname: Maldonado-Hernández
authors.forename: Laura Virginia
authors.initials: LV
authors.lastname: Prina-Ojeda
authors.forename: Irene
authors.initials: I
authors.lastname: Montalvo-Velarde
authors.forename: Martha
authors.initials: M
authors.lastname: Del Prado-Manríquez
authors.forename: María
authors.initials: M
authors.lastname: de Lourdes Barbosa-Cortés
authors.forename: Mariana
authors.initials: M
authors.lastname: Repetto-Madrid
mesh_terms: D000328:Adult; D019540:Area Under Curve; D015992:Body Mass Index; D001944:Breath Tests; D002247:Carbon Isotopes / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D005260:Female; D006801:Humans; D020138:Hyperhomocysteinemia / Q000175:diagnosis*; D008297:Male; D008715:Methionine / Q000032:analysis*; D042965:Methylenetetrahydrofolate Reductase (NADPH2) / Q000235:genetics; D008800:Mexico; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide; D012372:ROC Curve; D012680:Sensitivity and Specificity
chemical_list: D002247:Carbon Isotopes; D008715:Methionine; C573423:MTHFR protein, human; D042965:Methylenetetrahydrofolate Reductase (NADPH2)