title: A Multiplex Assay for the Diagnosis of Mucopolysaccharidoses and Mucolipidoses.
abstract: BACKGROUND
  Diagnosis of the mucopolysaccharidoses (MPSs) generally relies on an initial analysis of total glycosaminoglycan (GAG) excretion in urine. Often the dimethylmethylene blue dye-binding (DMB) assay is used, although false-negative results have been reported. We report a multiplexed diagnostic test with a high sensitivity for all MPSs and with the potential to identify patients with I-cell disease (ML II) and mucolipidosis III (ML III).
  
  
  METHODS
  Urine samples of 100 treatment naive MPS patients were collected and analyzed by the conventional DMB assay and a multiplex assay based on enzymatic digestion of heparan sulfate (HS), dermatan sulfate (DS) and keratan sulfate (KS) followed by quantification by LC-MS/MS. Specificity was calculated by analyzing urine samples from a cohort of 39 patients suspected for an inborn error of metabolism, including MPSs.
  
  
  RESULTS
  The MPS cohort consisted of 18 MPS I, 16 MPS II, 34 MPS III, 10 MPS IVA, 3 MPS IVB, 17 MPS VI and 2 MPS VII patients. All 100 patients were identified by the LC-MS/MS assay with typical patterns of elevation of HS, DS and KS, respectively (sensitivity 100%). DMB analysis of the urine was found to be in the normal range in 10 of the 100 patients (sensitivity 90%). Three out of the 39 patients were identified as false-positive, resulting in a specificity of the LS-MS/MS assay of 92%. For the DMB this was 97%. All three patients with MLII/MLIII had elevated GAGs in the LC-MS/MS assay while the DMB test was normal in 2 of them.
  
  
  CONCLUSIONS
  The multiplex LC-MS/MS assay provides a robust and very sensitive assay for the diagnosis of the complete spectrum of MPSs and has the potential to identify MPS related disorders such as MLII/MLIII. Its performance is superior to that of the conventional DMB assay.
authors.affiliation: Department of Pediatric Metabolic Diseases, Emma Children's Hospital and Amsterdam Lysosome Center 'Sphinx', Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Eveline J
authors.initials: EJ
authors.lastname: Langereis
authors.affiliation: Department of Pediatric Metabolic Diseases, Emma Children's Hospital and Amsterdam Lysosome Center 'Sphinx', Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; Laboratory for Genetic Metabolic Diseases, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Tom
authors.initials: T
authors.lastname: Wagemans
authors.affiliation: Laboratory for Genetic Metabolic Diseases, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Wim
authors.initials: W
authors.lastname: Kulik
authors.affiliation: Translational Metabolic Laboratory, Departments of Neurology & Laboratory Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands.
authors.forename: Dirk J
authors.initials: DJ
authors.lastname: Lefeber
authors.affiliation: Laboratory for Genetic Metabolic Diseases, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Henk
authors.initials: H
authors.lastname: van Lenthe
authors.affiliation: Department of Pediatrics, Center for Lysosomal and Metabolic Diseases, Erasmus Medical Center, Rotterdam, The Netherlands.
authors.forename: Esmee
authors.initials: E
authors.lastname: Oussoren
authors.affiliation: Department of Pediatrics, Center for Lysosomal and Metabolic Diseases, Erasmus Medical Center, Rotterdam, The Netherlands.
authors.forename: Ans T
authors.initials: AT
authors.lastname: van der Ploeg
authors.affiliation: Department of Clinical Genetics, Center for Lysosomal and Metabolic Diseases, Erasmus Medical Center, Rotterdam, The Netherlands.
authors.forename: George J
authors.initials: GJ
authors.lastname: Ruijter
authors.affiliation: Translational Metabolic Laboratory, Departments of Neurology & Laboratory Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands.
authors.forename: Ron A
authors.initials: RA
authors.lastname: Wevers
authors.affiliation: Department of Pediatric Metabolic Diseases, Emma Children's Hospital and Amsterdam Lysosome Center 'Sphinx', Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Frits A
authors.initials: FA
authors.lastname: Wijburg
authors.affiliation: Department of Pediatric Metabolic Diseases, Emma Children's Hospital and Amsterdam Lysosome Center 'Sphinx', Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; Laboratory for Genetic Metabolic Diseases, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Naomi
authors.initials: N
authors.lastname: van Vlies
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003871:Dermatan Sulfate / Q000302:isolation & purification* / Q000652:urine; D003937:Diagnosis, Differential; D006497:Heparan Sulfate / Q000302:isolation & purification* / Q000652:urine; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007632:Keratan Sulfate / Q000302:isolation & purification* / Q000652:urine; D008875:Middle Aged; D009081:Mucolipidoses / Q000175:diagnosis* / Q000652:urine; D009083:Mucopolysaccharidoses / Q000175:diagnosis* / Q000652:urine; D012680:Sensitivity and Specificity; D053719:Tandem Mass Spectrometry / Q000379:methods; D055815:Young Adult
chemical_list: D003871:Dermatan Sulfate; D006497:Heparan Sulfate; D007632:Keratan Sulfate