Special Instructions
This assay is available in New York State
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