090-21-1281-01

Metanephrines, Fractionated, Free, Plasma **

Use of an Epi-pen within last 7 days may produce inaccurate results.

Blood/ K3 EDTA (Lavender Top) 3 mL, 4 tubes

Plasma EDTA, minimum volume 4 mL
- Spin down within 2 hours of draw.
- Plasma must be separated from red blood cells within 2 hours of collection.

Plastic tube

Hemolysis: Mild OK; Gross reject
Lipemia: Mild OK; Gross OK
Icterus:Mild OK; Gross OK

Specimen Type	Temperature	Time
Plasma, EDTA	Ambient temperature	7 days
	Refrigerated, 2oC to 8oC	7 days
	Frozen (preferred)	14 days

090-21-1281-01

Metanephrines, Fractionated, Free, Plasma **

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

N/A **Sent out to MAYO, USA

14 days

MAYO Laboratory
Referral Lab Services, Laboratory Department 14160-2

090-21-1281-01

Metanephrines, Fractionated, Free, Plasma **

Pheochromocytoma is a rare, though potentially lethal, tumor of chromaffin cells of the adrenal medulla that produces episodes of hypertension with palpitations, severe headaches, and sweating ("spells"). Patients with pheochromocytoma may also be asymptomatic and present with sustained hypertension or an incidentally discovered adrenal mass. Pheochromocytomas and other tumors derived from neural crest cells (eg, paragangliomas and neuroblastomas) secrete catecholamines (epinephrine, norepinephrine, and dopamine). Metanephrine and normetanephrine (collectively referred to as metanephrines) are the 3-methoxy metabolites of epinephrine and norepinephrine, respectively. The metanephrines are stable metabolites and are cosecreted directly with catecholamines by pheochromocytomas and other neural crest tumors. This results in sustained elevations in plasma free metanephrine levels, making them more sensitive and specific than plasma catecholamines in the identification of pheochromocytoma patients. Metanephrine and normetanephrine are both further metabolized to conjugated metanephrines and vanillylmandelic acid.

METANEPHRINE, FREE <0.50 nmol/L
NORMETANEPHRINE, FREE <0.90 nmol/L

In the normal population, plasma metanephrine and normetanephrine levels are low, but in patients with pheochromocytoma or paragangliomas, the concentrations may be significantly elevated. This is due to the relatively long half-life of these compounds, ongoing secretion by the tumors and, to a lesser degree, peripheral conversion of tumor-secreted catecholamines into metanephrines. Elevated results are reported with appropriate comments.

www.mayomedicallaboratories.com (Retrieved: 24 Jan 2019)