Diagnosis of aromatic l-amino acid decarboxylase deficiency by measuring 3-O-methyldopa concentrations in dried blood spots

• Published in: Clinica chimica acta 2014-04, Vol.431, p.19-22
• Main Authors: Chen, Pin-Wen, Lee, Ni-Chung, Chien, Yin-Hsiu, Wu, Jia-Yun, Wang, Ping-Chun, Hwu, Wuh-Liang
• Format: Article
• Language: English
• Subjects: 3-O-methyldopa; Amino Acid Metabolism, Inborn Errors - blood; Amino Acid Metabolism, Inborn Errors - diagnosis; Aromatic L-amino-acid decarboxylase; Aromatic-L-Amino-Acid Decarboxylases - blood; Aromatic-L-Amino-Acid Decarboxylases - deficiency; Calibration; Child; Child, Preschool; Chromatography, High Pressure Liquid; Dihydroxyphenylalanine - analogs & derivatives; Dihydroxyphenylalanine - blood; Dried Blood Spot Testing; Humans; Infant; Infant, Newborn; Liquid chromatography–tandem mass spectrometry; Neonatal Screening; Neurotransmitter; Quality Control; Reference Standards; Reproducibility of Results; Tandem Mass Spectrometry; Tyrosine - analogs & derivatives
• ISSN: 0009-8981; 1873-3492
• DOI: 10.1016/j.cca.2014.01.034

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. 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). 3-OMD in DBSs was shown to be stable for more than 28days 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. 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. •3-O-methyldopa (3-OMD) is a catabolic product of l-dopa.•3-OMD accumulates in patients with AADC deficiency.•3-OMD levels in dried blood spot (DBS) are stable for more than 28days.•3-OMD levels are highly elevated in newborns and children with AADC deficiency.•3-OMD level in DBS can be used for newborn screening of AADC deficiency