title: Diagnosis of aromatic L-amino acid decarboxylase deficiency by measuring 3-O-methyldopa concentrations in dried blood spots.
abstract: BACKGROUND
  Inherited defects that affect the synthesis or metabolism of neurotransmitters cause severe motor dysfunction. The diagnosis of these diseases, including aromatic L-amino-acid decarboxylase (AADC) deficiency, typically requires cerebrospinal fluid (CSF) neurotransmitter analysis. However, 3-O-methyldopa (3-OMD), which is a catabolic product of L-dopa that accumulates in individuals with AADC deficiency, can be detected in blood.
  
  
  METHODS
  3-OMD concentrations were measured in dried blood spots (DBSs). One 3.2-mm punch was eluted with 90% methanol containing a deuterated internal standard (3-OMD-d3), and then analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS).
  
  
  RESULTS
  3-OMD in DBSs was shown to be stable for more than 28 days at 37°C. We measured DBS 3-OMD concentrations in controls and patients with AADC deficiency. 3-OMD concentrations in normal newborns and children decreased with age. Patients with AADC deficiency revealed >15-fold increase of DBS 3-OMD concentrations. Archive newborn screening DBS samples, obtained from 6 patients with AADC deficiency, revealed more than 19-fold increase of 3-OMD concentrations.
  
  
  CONCLUSIONS
  We demonstrated that DBS 3-OMD concentrations were highly elevated in newborns and children with AADC deficiency. Because 3-OMD is stable in DBS, this method can be used for both high risk and newborn screening of AADC deficiency.
authors: Department of Medical Genetics and Pediatrics, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan.
authors: Pin-Wen
authors: PW
authors: Chen
authors: Department of Medical Genetics and Pediatrics, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan.
authors: Ni-Chung
authors: NC
authors: Lee
authors: Department of Medical Genetics and Pediatrics, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan.
authors: Yin-Hsiu
authors: YH
authors: Chien
authors: Department of Medical Genetics and Pediatrics, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan.
authors: Jia-Yun
authors: JY
authors: Wu
authors: Department of Medical Genetics and Pediatrics, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan.
authors: Ping-Chun
authors: PC
authors: Wang
authors: Department of Medical Genetics and Pediatrics, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan. Electronic address: hwuwlntu@ntu.edu.tw.
authors: Wuh-Liang
authors: WL
authors: Hwu
mesh_terms: D000592:Amino Acid Metabolism, Inborn Errors / Q000097:blood / Q000175:diagnosis*; D001142:Aromatic-L-Amino-Acid Decarboxylases / Q000097:blood / Q000172:deficiency*; D002138:Calibration; D002648:Child; D002675:Child, Preschool; D002851:Chromatography, High Pressure Liquid; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives* / Q000097:blood; D059788:Dried Blood Spot Testing; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D015997:Neonatal Screening; D011786:Quality Control; D012015:Reference Standards; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry; D014443:Tyrosine / Q000031:analogs & derivatives
chemical_list: D014443:Tyrosine; D004295:Dihydroxyphenylalanine; D001142:Aromatic-L-Amino-Acid Decarboxylases; C008404:3-methoxytyrosine
keywords: 3-O-methyldopa; Aromatic L-amino-acid decarboxylase; Liquid chromatography–tandem mass spectrometry; Neurotransmitter