Metanephrines, Fractionated, Free, LC/MS/MS, Plasma

CPT Code(s)

83835

Includes

Metanephrine, Normetanephrine, and Total Metanephrine

Patient Preparation

Patient should avoid alcohol, coffee, tea, tobacco and strenuous exercise prior to collection. Overnight fasting is preferred. Patients should be relaxed in either a supine or upright position before blood is drawn.

Preferred Specimen(s)

2.5 mL plasma collected in an EDTA (lavender-top) tube

Minimum Volume

1.5 mL

Collection Instructions

Draw specimen in a pre-chilled EDTA lavender-top Vacutainer®. The whole blood sample should be kept on wet ice until centrifuged (preferably at 4° C) to separate the plasma within 2 hours of venipuncture. After centrifugation, the plasma should be transferred to a plastic, leak-proof vial and immediately refrigerated.

Transport Temperature

Refrigerated (cold packs)

Specimen Stability

Room temperature: 4 hours

Refrigerated: 14 days

Frozen: 14 days

Reject Criteria

Heparinized plasma • Serum • CSF • Urine

Methodology

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

Performing Laboratory

Quest Diagnostics Nichols Institute

33608 Ortega Highway

San Juan Capistrano, CA 92690-6130

Setup Schedule

Set up: Mon-Fri; Report available: 3-5 days

Limitations

False-positive results have been observed in patients with either chronic kidney disease or hypertension.

Reference Range(s)

Metanephrine, Free:        < OR = 57 pg/mL

Normetanephrine, Free:  < OR = 148

Total, Free (MN + NMN):  < OR = 205 pg/mL



Elevations > 4-fold upper reference range: strongly suggestive of a

pheochromocytoma(1). Elevations >1 - 4-fold upper reference range:

significant but not diagnostic, may be due to medications or stress. Suggest

running 24 hr urine fractionated metanephrines and serum Chromogranin A for confirmation.

Clinical Significance

Normetanephrine (NM) and metanephrine (MN) are the extra-neuronal catechol-o-methyl transferase (COMT) metabolites of the catecholamines norepinephrine and epinephrine, respectively. Measurement of plasma metanephrines is more sensitive (but may be less specific) than measurement of catecholamines for the detection of pheochromocytoma. Proper interpretation of results requires awareness of recent medication/drug history (e.g., antyhypertensive agents, alcohol, cocaine) and other pre-analytical factors (e.g., stress, severe congestive heart failure, myocardial infarction) that influence release of catecholamines and metanephrines.