ARUP's Laboratory Test Directory

Metanephrines, Plasma (Free) : 0050184

Mnemonic: META PF

Ordering Recommendation: First-line test in suspected pheochromocytoma.
Methodology: Quantitative Liquid Chromatography-Tandem Mass Spectrometry
Performed: Sun-Sat
Reported: 2-6 days
Specimen Required: Patient Prep: Epinephrine and epinephrine-like drugs may affect results, and should be discontinued for at least 72 hours prior to specimen collection, if possible. Collect the specimen after the patient has rested for 15 minutes
in a supine position.

Collect: Lavender (EDTA), pink (K2EDTA), or green (sodium or lithium heparin). Collect specimen and place in ice bath.

Specimen Preparation: Centrifuge within 1 hour. Transfer 2 mL plasma to an ARUP Standard Transport Tube and freeze immediately. (Min: 1 mL) Avoid hemolysis.

Storage/Transport Temperature: CRITICAL FROZEN. Separate specimens must be submitted when multiple tests are ordered.

Remarks:

Unacceptable Conditions: Plasma separator tubes. Body fluids other than EDTA or heparinized plasma. Non-frozen or icteric specimens.

Stability (collection to initiation of testing): After separation from cells: Ambient: Unacceptable; Refrigerated: Unacceptable; Frozen: 1 month
Reference Interval:
Normetanephrine: 0.0-0.89 nmol/L
Metanephrine: 0.0-0.49 nmol/L
Interpretive Data: : This test is useful in the detection of pheochromocytoma, a rare neuroendocrine tumor. The majority of patients with pheochromocytoma have a plasma normetanephrine concentration in excess of 2.2 nmol/L and/or a metanephrine concentration in excess of 1.1 nmol/L. Increased concentrations of these analytes serve as confirmation for diagnosis. Patients with essential hypertension and plasma concentrations of normetanephrine below 0.9 nmol/L and/or a metanephrine concentration below 0.5 nmol/L, can be excluded from further testing. If clinical suspicion remains, repeat testing or testing for metanephrines in a 24-hr. urine specimen should be considered.
Note: Isoetharine, isoproterenol, 3,4-methylenedioxyamphetamine (MDA), and 3,4-methylenedioxymethamphetamine (MDMA) are known to interfere in this test.

Many drugs/medications, including over-the-counter and herbal products, can interfere with test results. Testing for all potential interactions is not possible.  If the patient is taking a drug not listed as an interferent, its potential effect on test results is unknown. If test results are inconsistent with clinical evidence, drug interference should be considered. If appropriate, the patient should discontinue the potential interferent for 48-72 hours and a new sample collected for retesting.
CPT Code(s): 83835
Cross References: Metanephrine (Metanephrines, Plasma (Free)), Metanephrines, Fractionated (Metanephrines, Plasma (Free)), Normetanephrine (Metanephrines, Plasma (Free)), Quantitative Metanephrines (Metanephrines, Plasma (Free))