title: Sulfatide Analysis by Mass Spectrometry for Screening of Metachromatic Leukodystrophy in Dried Blood and Urine Samples.
abstract: BACKGROUND
  Metachromatic leukodystrophy (MLD) is an autosomal recessive disorder caused by deficiency in arylsulfatase A activity, leading to accumulation of sulfatide substrates. Diagnostic and monitoring procedures include demonstration of reduced arylsulfatase A activity in peripheral blood leukocytes or detection of sulfatides in urine. However, the development of a screening test is challenging because of instability of the enzyme in dried blood spots (DBS), the widespread occurrence of pseudodeficiency alleles, and the lack of available urine samples from newborn screening programs.
  
  
  METHODS
  We measured individual sulfatide profiles in DBS and dried urine spots (DUS) from MLD patients with LC-MS/MS to identify markers with the discriminatory power to differentiate affected individuals from controls. We also developed a method for converting all sulfatide molecular species into a single species, allowing quantification in positive-ion mode upon derivatization.
  
  
  RESULTS
  In DBS from MLD patients, we found up to 23.2-fold and 5.1-fold differences in total sulfatide concentrations for early- and late-onset MLD, respectively, compared with controls and pseudodeficiencies. Corresponding DUS revealed up to 164-fold and 78-fold differences for early- and late-onset MLD patient samples compared with controls. The use of sulfatides converted to a single species simplified the analysis and increased detection sensitivity in positive-ion mode, providing a second option for sulfatide analysis.
  
  
  CONCLUSIONS
  This study of sulfatides in DBS and DUS suggests the feasibility of the mass spectrometry method for newborn screening of MLD and sets the stage for a larger-scale newborn screening pilot study.
authors.affiliation: Department of Chemistry, gelb@chem.washington.edu spacil@u.washington.edu.
authors.forename: Zdenek
authors.initials: Z
authors.lastname: Spacil
authors.affiliation: Department of Chemistry.
authors.forename: Arun
authors.initials: A
authors.lastname: Babu Kumar
authors.affiliation: Department of Chemistry.
authors.forename: Hsuan-Chieh
authors.initials: HC
authors.lastname: Liao
authors.affiliation: Clinical Research Center, Centre Hospitalier Universitaire de Sherbrooke, and Université de Sherbrooke, Sherbrooke, Quebec, Canada;
authors.forename: Christiane
authors.initials: C
authors.lastname: Auray-Blais
authors.affiliation: National Referral Laboratory, Genetics and Molecular Pathology, South Australia Pathology, Women's and Children's Hospital, Adelaide, Australia;
authors.forename: Samantha
authors.initials: S
authors.lastname: Stark
authors.affiliation: MLD Foundation, West Linn, OR.
authors.forename: Teryn R
authors.initials: TR
authors.lastname: Suhr
authors.affiliation: Department of Pediatrics, and.
authors.forename: C Ronald
authors.initials: CR
authors.lastname: Scott
authors.affiliation: Department of Chemistry.
authors.forename: Frantisek
authors.initials: F
authors.lastname: Turecek
authors.affiliation: Department of Chemistry, Department of Biochemistry, University of Washington, Seattle, WA; gelb@chem.washington.edu spacil@u.washington.edu.
authors.forename: Michael H
authors.initials: MH
authors.lastname: Gelb
mesh_terms: D002851:Chromatography, High Pressure Liquid; D059788:Dried Blood Spot Testing; D006801:Humans; D007231:Infant, Newborn; D007966:Leukodystrophy, Metachromatic / Q000097:blood* / Q000652:urine*; D013058:Mass Spectrometry; D015997:Neonatal Screening; D012680:Sensitivity and Specificity; D013433:Sulfoglycosphingolipids / Q000097:blood* / Q000652:urine*
chemical_list: D013433:Sulfoglycosphingolipids