title: Simultaneous determination of cystathionine, total homocysteine, and methionine in dried blood spots by liquid chromatography/tandem mass spectrometry and its utility for the management of patients with homocystinuria.
abstract: BACKGROUND
  Disorders of homocysteine and B-vitamin metabolism represent a significant problem in clinical practice. Establishing the diagnosis requires specialized tests with demanding preanalytical requirements. To advance the detection of patients with these disorders, we developed a method for the simultaneous determination of cystathionine (Cysta), methionine (Met) and total homocysteine (tHcy) in dried blood spots (DBSs).
  
  
  METHODS
  A punch from a DBS sample was mixed with a solution of isotopically labeled internal standards, and analytes were extracted using methanol/0.1% formic acid/0.5mol/L dithiothreitol. The extract was injected into an LC-MS/MS system operating in MRM mode.
  
  
  RESULTS
  The analytical performance of the method employing DBS is adequate for its purpose and the type of sample. Compared with Cysta, tHcy and Met plasma levels, our method exhibited a negative bias between -3.8% and -42.2% due to the lower concentrations of these analytes in erythrocytes. The tHcy level and the Met/Cysta ratio in DBS enabled the clear detection of 12 patients with disorders of transsulfuration and with genetic and nutritional remethylation defects.
  
  
  CONCLUSIONS
  The ease of collecting and transporting DBS samples may advance diagnostic procedures in patients with neuropsychiatric disorders and thromboembolism. Consequently, this approach may facilitate detection and simplify the monitoring of patients with homocystinuria.
authors.affiliation: Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Czech Republic.
authors.forename: Josef
authors.initials: J
authors.lastname: Bártl
authors.affiliation: Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Chrastina
authors.affiliation: Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Czech Republic.
authors.forename: Jakub
authors.initials: J
authors.lastname: Krijt
authors.affiliation: Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Czech Republic.
authors.forename: Jakub
authors.initials: J
authors.lastname: Hodík
authors.affiliation: Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Czech Republic.
authors.forename: Karolína
authors.initials: K
authors.lastname: Pešková
authors.affiliation: Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Czech Republic. Electronic address: Viktor.Kozich@vfn.cz.
authors.forename: Viktor
authors.initials: V
authors.lastname: Kožich
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D002853:Chromatography, Liquid / Q000379:methods / Q000706:statistics & numerical data; D003540:Cystathionine / Q000097:blood*; D019468:Disease Management; D059788:Dried Blood Spot Testing / Q000379:methods* / Q000706:statistics & numerical data; D005260:Female; D006710:Homocysteine / Q000097:blood*; D006712:Homocystinuria / Q000097:blood* / Q000175:diagnosis; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008715:Methionine / Q000097:blood*; D053719:Tandem Mass Spectrometry / Q000379:methods* / Q000706:statistics & numerical data
chemical_list: D006710:Homocysteine; D003540:Cystathionine; D008715:Methionine
keywords: Cystathionine; Dried blood spots; Homocysteine; LC–MS/MS; Methionine; Therapy monitoring