Chien YH, Chen PW, Lee NC, Hsieh WS, Chiu PC, Hwu WL, Tsai FJ, Lin SP, Chu SY, Jong YJ, Chao MC. 3-O-methyldopa levels in newborns: Result of newborn screening for aromatic l-amino-acid decarboxylase deficiency. Mol Genet Metab. 2016 Aug;118(4):259-63.
The diagnosis of aromatic l-amino-acid decarboxylase (AADC) deficiency is often delayed because a cerebrospinal fluid analysis is required to detect a neurotransmitter deficiency. We here demonstrated that an elevated concentration of l-dopa metabolite 3-O-methyldopa (3-OMD) in dried blood spots could be integrated into newborn screening program to precisely predict AADC deficiency.
After obtaining parental consent, an additional spot was punched from newborn filter paper, eluted, cleaned, and analyzed by tandem mass spectrometry. Newborns with a 3-OMD concentration exceeding 500ng/mL were referred for confirmatory testing.
From September 2013 to December 2015, 127,987 newborns were screened for AADC deficiency. The mean 3-OMD concentration in these newborns was 88.08ng/mL (SD=27.74ng/mL). Four newborns exhibited an elevated 3-OMD concentration (range, 939-3241ng/mL). All four newborns were confirmed to carry two pathologic DDC mutations, indicating an incidence of AADC deficiency of 1:32,000. During the follow-up period, three patients developed typical symptoms of AADC deficiency. Among 16 newborns with mildly elevated 3-OMD levels, six were heterozygous for the DDC IVS6+4A>T mutation.
Newborn screening of AADC deficiency was achieved with a 100% positive-predictive rate. An association for gestational age could be further elucidated.
Chen PW, Lee NC, Chien YH, Wu JY, Wang PC, Hwu WL. Diagnosis of aromatic L-amino acid decarboxylase deficiency by measuring 3-O-methyldopa concentrations in dried blood spots. Clin Chim Acta. 2014 Apr 20;431:19-22.
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 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.
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.