title: Creatine transporter deficiency: prevalence among patients with mental retardation and pitfalls in metabolite screening.
abstract: OBJECTIVE
  To report the prevalence of creatine transporter deficiency in males with mental retardation and to study whether a protein-rich food intake might be a potential diagnostic pitfall.
  
  
  METHODS
  We determined creatine/creatinine ratio in urine samples from 1600 unrelated male patients with mental retardation and/or autism. Urine creatine was analyzed by HPLC-MS/MS.
  
  
  RESULTS
  Thirty-three of 1600 cases showed increased urine creatine/creatinine ratio. Four out of these thirty-three cases were definitively diagnosed with creatine transporter deficiency, while the other 29 were false positive results. Significantly higher values were observed for urine Cr/Crn ratio in healthy volunteers after a meal based on beef or oily fish as compared to eggs, pasta or salad (Wilcoxon test: p<0.005).
  
  
  CONCLUSIONS
  False positive results may be observed in biochemical screening for creatine transporter deficiency, and they may be due to intake of meals rich in creatine prior to urine samples analysis.
authors.affiliation: Institut de Bioquímica Clínica, Servicio de Bioquímica y Genética Molecular, Hospital Clínic and Centre for Biomedical Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Barcelona, Spain.
authors.forename: Angela
authors.initials: A
authors.lastname: Arias
authors.forename: Marc
authors.initials: M
authors.lastname: Corbella
authors.forename: Carmen
authors.initials: C
authors.lastname: Fons
authors.forename: Angela
authors.initials: A
authors.lastname: Sempere
authors.forename: Judit
authors.initials: J
authors.lastname: García-Villoria
authors.forename: Aida
authors.initials: A
authors.lastname: Ormazabal
authors.forename: Pilar
authors.initials: P
authors.lastname: Poo
authors.forename: Mercé
authors.initials: M
authors.lastname: Pineda
authors.forename: María Antonia
authors.initials: MA
authors.lastname: Vilaseca
authors.forename: Jaume
authors.initials: J
authors.lastname: Campistol
authors.forename: Paz
authors.initials: P
authors.lastname: Briones
authors.forename: Teresa
authors.initials: T
authors.lastname: Pàmpols
authors.forename: Gajja S
authors.initials: GS
authors.lastname: Salomons
authors.forename: Antonia
authors.initials: A
authors.lastname: Ribes
authors.forename: Rafael
authors.initials: R
authors.lastname: Artuch
mesh_terms: D001321:Autistic Disorder / Q000235:genetics / Q000652:urine; D002648:Child; D002675:Child, Preschool; D003401:Creatine / Q000652:urine; D003404:Creatinine / Q000652:urine; D005998:Glycine / Q000031:analogs & derivatives / Q000378:metabolism; D006801:Humans; D007223:Infant; D008607:Intellectual Disability / Q000235:genetics / Q000652:urine*; D008297:Male; D008403:Mass Screening / Q000379:methods*; D026901:Membrane Transport Proteins / Q000172:deficiency* / Q000235:genetics; D008661:Metabolism, Inborn Errors / Q000175:diagnosis* / Q000235:genetics / Q000378:metabolism; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity