title: Evaluation of α-iduronidase in dried blood spots is an accurate tool for mucopolysaccharidosis I diagnosis.
abstract: BACKGROUND
  Mucopolysaccharidosis type I (MPS I) is caused by a deficiency of the α-L-iduronidase (IDUA), which leads to the accumulation of glycosaminoglycans in lysosomes. MPS I patients present a spectrum ranging from a severe to an attenuated phenotype. Once clinical suspicion is present, diagnosis of MPS I can be performed by enzyme activity determination and/or molecular analysis. The aim of this study was to establish a reference interval value to IDUA activity using a dried blood spots (DBS) assay and to evaluate whether this assay could be a secure tool to diagnose MPS I patients.
  
  
  RESULTS
  IDUA activity range on HV DBS samples were 1.40-7.78 µmol/l blood/hr. Regarding the validation group, 11 of the 36 individuals clinically suspected of MPS I had the diagnosis confirmed by DBS and reference assay (leukocytes). When we considered the new proposed cutoff value of 1.5 µmol/l blood/hr, the sensitivity, specificity, and predictive values were 100%.
  
  
  CONCLUSIONS
  Our results strongly suggest that the determination of IDUA activity using a DBS assay is a secure tool for MPS I diagnosis. However, it is extremely important to assure that all recommendations for collection, transport, and storage are correctly followed to guarantee the quality of the samples.
authors.affiliation: Department of Pediatrics, Universidade Federal de São Paulo, São Paulo, Brazil.
authors.forename: Karen B
authors.initials: KB
authors.lastname: Müller
authors.forename: Vanessa G
authors.initials: VG
authors.lastname: Pereira
authors.forename: Ana M
authors.initials: AM
authors.lastname: Martins
authors.forename: Vânia
authors.initials: V
authors.lastname: D'Almeida
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001774:Blood Chemical Analysis / Q000379:methods; D001800:Blood Specimen Collection / Q000379:methods; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007068:Iduronidase / Q000097:blood*; D007962:Leukocytes; D008297:Male; D008875:Middle Aged; D008059:Mucopolysaccharidosis I / Q000175:diagnosis / Q000201:enzymology*; D012372:ROC Curve; D015203:Reproducibility of Results
chemical_list: D007068:Iduronidase