title: Direct tandem mass spectrometric profiling of sulfatides in dry urinary samples for screening of metachromatic leukodystrophy.
abstract: BACKGROUND
  Prediagnostic steps in suspected metachromatic leukodystrophy (MLD) rely on clinical chemical methods other than enzyme assays. We report a new diagnostic method which evaluates changes in the spectrum of molecular types of sulfatides (3-O-sulfogalactosyl ceramides) in MLD urine.
  
  
  METHODS
  The procedure allows isolation of urinary sulfatides by solid-phase extraction on DEAE-cellulose membranes, transportation of a dry membrane followed by elution and tandem mass spectrometry (MS/MS) analysis in the clinical laboratory. Major sulfatide isoforms are normalized to the least variable component of the spectrum, which is the indigenous C18:0 isoform. This procedure does not require the use of specific internal standards and minimizes errors caused by sample preparation and measurement.
  
  
  RESULTS
  Urinary sulfatides were analyzed in a set of 21 samples from patients affected by sulfatidosis. The combined abundance of the five most elevated isoforms, C22:0, C22:0-OH, C24:0, C24:1-OH, and C24:0-OH sulfatides, was found to give the greatest distinction between MLD-affected patients and a control group.
  
  
  CONCLUSIONS
  The method avoids transportation of liquid urine samples and generates stable membrane-bound sulfatide samples that can be stored at ambient temperature. MS/MS sulfatide profiling targeted on the most MLD-representative isoforms is simple with robust results and is suitable for screening.
authors.affiliation: Institute of Inherited Metabolic Diseases, First Faculty of Medicine and General Teaching Hospital, Charles University, 128 08 Prague, Czech Republic.
authors.forename: Ladislav
authors.initials: L
authors.lastname: Kuchař
authors.forename: Befekadu
authors.initials: B
authors.lastname: Asfaw
authors.forename: Helena
authors.initials: H
authors.lastname: Poupětová
authors.forename: Jitka
authors.initials: J
authors.lastname: Honzíková
authors.forename: František
authors.initials: F
authors.lastname: Tureček
authors.forename: Jana
authors.initials: J
authors.lastname: Ledvinová
mesh_terms: D000293:Adolescent; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D003636:DEAE-Cellulose; D003890:Desiccation; D005260:Female; D006801:Humans; D007223:Infant; D007966:Leukodystrophy, Metachromatic / Q000175:diagnosis / Q000652:urine*; D008297:Male; D008567:Membranes, Artificial; D008875:Middle Aged; D012015:Reference Standards; D052616:Solid Phase Extraction; D013048:Specimen Handling / Q000592:standards*; D013433:Sulfoglycosphingolipids / Q000652:urine*; D053719:Tandem Mass Spectrometry
chemical_list: D008567:Membranes, Artificial; D013433:Sulfoglycosphingolipids; D003636:DEAE-Cellulose
keywords: ASA; CV; DEAE; DEAE-cellulose membrane; DUS; Diethylaminoethyl; Dry urinary samples; IPN; Isoforms; MLD; MS/MS; PTFE; Psap-d; S/N; SRM; Screening for metachromatic leukodystrophy; Tandem mass spectrometry; Urinary sulfatide; arylsulfatase A; coefficient of variation; dry urinary sample; isoform profile number (ratio of the sum of the major five isoforms and the C18:0 sulfatide); metachromatic leukodystrophy; polytetrafluoroethylene; prosaposin deficiency; selected reaction monitoring; signal to noise ratio; tandem mass spectrometry