title: Measurement of psychosine in dried blood spots--a possible improvement to newborn screening programs for Krabbe disease.
abstract: BACKGROUND
  Newborn screening (NBS) for Krabbe disease (KD) in New York and Missouri is conducted by measuring galactocerebrosidase (GALC) activity using tandem mass spectrometry (MS/MS). These NBS efforts have shown that the incidence of KD is unexpectedly low (1:400,000) while many individuals (ca. 1:6000) with reduced GALC activity and genotypes of uncertain significance are detected and subjected to follow up testing. Psychosine (PSY) is a putative marker of KD progression and can be measured in dried blood spots (DBS). We sought to determine the role that PSY levels play in NBS for KD, follow up, and treatment monitoring.
  
  
  METHODS
  PSY was eluted from DBS with methanol containing N,N-dimethyl-D-erythro-sphingosine as internal standard (IS). Liquid chromatography-MS/MS was conducted over 17 minutes in the multiple reaction monitoring positive mode to follow the precursor to product species transitions for PSY and IS. Separation of the structural isomers PSY and glucosylsphingosine was accomplished by hydrophilic interaction liquid chromatography.
  
  
  RESULTS
  Pre-analytical and analytical factors were studied and revealed satisfactory results. PSY was also measured in DBS collected from controls (range: <8 nmol/L, N = 220), KD patients at various disease stages (range: 8-112, N = 26), and GALC mutation carriers (range: <15 nmol/L, N = 18).
  
  
  CONCLUSIONS
  PSY measurement in DBS could serve as a 2nd tier assay in NBS for KD, simplify and reduce the cost of follow up protocols, help determine disease progression, and be used to monitor KD patients following hematopoietic stem cell transplantation. However, additional chronological measurements of PSY in KD patients are required to confirm these possibilities.
authors.affiliation: Biochemical Genetics Laboratory, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN, 55905, USA.
authors.forename: Coleman T
authors.initials: CT
authors.lastname: Turgeon
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Orsini
authors.forename: Karen A
authors.initials: KA
authors.lastname: Sanders
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Magera
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Langan
authors.forename: Maria L
authors.initials: ML
authors.lastname: Escolar
authors.forename: Patricia
authors.initials: P
authors.lastname: Duffner
authors.forename: Devin
authors.initials: D
authors.lastname: Oglesbee
authors.forename: Dimitar
authors.initials: D
authors.lastname: Gavrilov
authors.forename: Silvia
authors.initials: S
authors.lastname: Tortorelli
authors.forename: Piero
authors.initials: P
authors.lastname: Rinaldo
authors.forename: Kimiyo
authors.initials: K
authors.lastname: Raymond
authors.forename: Dietrich
authors.initials: D
authors.lastname: Matern
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D059788:Dried Blood Spot Testing / Q000592:standards; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007965:Leukodystrophy, Globoid Cell / Q000097:blood / Q000175:diagnosis*; D057230:Limit of Detection; D008875:Middle Aged; D015997:Neonatal Screening / Q000379:methods* / Q000592:standards; D011609:Psychosine / Q000032:analysis / Q000097:blood*; D058996:Quality Improvement; D012016:Reference Values; D015203:Reproducibility of Results; D055815:Young Adult
chemical_list: D011609:Psychosine