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Metanephrines Fractionated Free, Plasma

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Test Codes

EPIC: LAB821, Beaker: Meta Plasma, MAYO: PMET

Department

Send Outs

Specimen Collection Criteria

Collect (preferred): One Pink-top (K₂EDTA) tube.

Also Acceptable: One Lavender-top (EDTA) tube.

Send specimen to the Laboratory immediately after collection for processing.

Physician Office/Draw Specimen Preparation

Centrifuge to separate plasma from cells within 2 hours of collection. Transfer plasma to plastic transport tube and freeze (-20°C/-4°F or below) immediately.

Preparation for Courier Transport

Transport: 1.0 mL plasma, frozen (-20°C/-4°F or below). (Minimum: 0.3 mL)

Rejection Criteria

• Hemolyzed specimens.
• Specimens not collected and processed as indicated.

Inpatient Specimen Preparation

Transport specimens to the Laboratory immediately after collection.

In-Lab Processing

Centrifuge to separate plasma from cells within 2 hours of collection. Transfer plasma to plastic transport tube and freeze (-20°C/-4°F or below) immediately.

Transport: 1.0 mL plasma, frozen (-20°C/-4°F or below). (Minimum: 0.3 mL)

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): Unacceptable
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 14 days

Specimen Storage in Department Prior to Disposal:

Specimen retention time is determined by the policy of the reference laboratory. Contact the Send Outs Laboratory with any questions.

Laboratory

Sent to Mayo Medical Laboratories, Rochester, MN.

Performed

Monday – Saturday.
Results available in 3-5 days.

Reference Range

Metanephrine, Free: Less than 0.50 nmol/L.
Normetanephrine, Free: Less than 0.90 nmol/L.

Test Methodology

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

Interpretation

Pheochromocytoma is a rare tumor of neural crest cell origin that can present with episodic or sustained hypertension, palpitations, severe headaches, sweating, or they can be asymptomatic. Phenochromocytomas and other tumors derived from neural crest cells (i.e.-paragangliomas and neuroblastomas) secrete catecholamines (epinephrine, norepinephrine and dopamine) and/or their metabolites (metanephrine, normetanephrine-collectively called metanephrines). The metanephrines are stable metabolites and are co-secreted directly with catecholamines. This results in sustained levels, making them more sensitive and specific than plasma catecholamines in the identification of pheochromocytomas. The metanephrines can be further metabolized to vanillylmandelic acid (VMA).

Substances that increase endogenous catecholamine levels can result in borderline elevations of plasma metanephrines. These include 1) monoamine oxidase inhibitors particularly when combined with tyrosine-rich foods such as nuts, bananas, cheese, 2) catecholamine reuptake inhibitors such as cocaine or cocaine derivatives, includes some local anesthetics and antiarrhythmic drugs 3) some anesthetic gases such as halothane 4) withdrawal from sedative drugs, includes alcohol, benzodiazepines, opioids, and some central acting anthypertensive medications such as clonidine.

Artifactually low levels of plasma metanephrines may be observed in patients receiving metyrosine.

Clinical Utility

This assay is most useful in screening for tumors derived from neural crest cells such as pheochromocytomas and paragangliomas.

CPT Codes

83835

Contacts

Last Updated

8/26/2024