Special Instructions
This assay is available in New York State
Test orders should now be placed through Labcorp using test code 620176
Specimen Requirements
Specimen
Plasma
Volume
1.0 mL
Minimum Volume
0.5 mL
Container
Sterile screw capped vial
Collection
Blood: Collect 2-4 milliliters of blood in EDTA (purple top) or sodium heparin (green top) tube. Remove plasma and freeze at -20°Celsius or below. Preferred volume: 1.0 milliliter, minimum volume: 0.5 milliliter
Storage Instructions
Freeze as soon as possible after collection; Ship within 24 hours. Ship samples priority overnight on 3-4 lbs of dry ice. Sample must arrive in our lab Monday - Saturday. We do NOT accept Sunday or holiday deliveries.
Stability Requirements
Room Temperature: Not stable; Refrigerated: not stable; Frozen: indefinitely @ -20C, Indefinitely @ -80C; Freeze/Thaw: None
Causes for Rejection
Sample received thawed; Sample hemolyzed or bloody
Test Details
Use
Plasma 3-0-methyldopa is useful for the diagnosis of Aromatic L-amino acid decarboxylase (AADC) deficiency, a pyridoxal 5’-phosphate dependent enzyme responsible for the formation of dopamine and serotonin. AADC deficiency is a congenital autosomal recessive metabolic disorder that causes hypotonia, hypokinesia, oculogyric crises, and signs of autonomic dysfunction beginning in infancy. In AADC deficiency, L-dopa accumulates and can be methylated by catechol O-methyltransferase using S-adenosylmethionine as the methyl donor to form 3-O-methyldopa (3-OMD). 3-OMD is more stable than L-dopa and is elevated in plasma from patients with AADC deficiency.
Methodology
LC/MS/MS