3-O-Methyldopa (Plasma)

18 days

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Storage Instructions: Freeze as soon as possible after collection. Store all samples at -80C until shipment. If -80C freezer is unavailable, store the samples at -20C and submit the shipment as soon as possible.

Accredited Laboratory Partner

Plasma 3-0-methyldopa (3-OMD) 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. This test may also support interpretation of variants of uncertain significance (VUS) identified through genetic testing, including next- generation sequencing, in the DDC gene and genes involved in pyridoxal 5'-phosphate metabolism. 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-OMD. 3-OMD is more stable than L-dopa and is elevated in plasma from patients with AADC deficiency. Plasma 3-OMD may also be useful for assessing compliance and therapeutic monitoring of treatment with levodopa.

Plasma

0.5 mL

Frozen plasma from green-top (lithium heparin) tube, and frozen plasma from lavender-top (EDTA) tube

No special preparation is required for this test. You may eat, drink, and take your medications as normal, unless instructed otherwise by your healthcare provider.

Separate plasma from cells. Transfer specimen to plastic transport tube before freezing.