Metanephrines, Plasma (Free)

Also known as: META PF

Clinical Use

Use

This test is useful in the detection of pheochromocytoma, a rare neuroendocrine tumor. It measures the plasma concentrations of normetanephrine and metanephrine, metabolites of catecholamines, which are typically elevated in patients with pheochromocytoma. 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 a metanephrine concentration below 0.5 nmol/L can be excluded from further testing.

Special Instructions

Not provided.

Limitations

The test is sensitive to interference from various substances including isoetharine, isoproterenol, 3,4-methylenedioxyamphetamine (MDA), and 3,4-methylenedioxymethamphetamine (MDMA). Additionally, many drugs/medications, including over-the-counter and herbal products, can interfere with test results, and testing for all potential interactions is not possible. Therefore, it is recommended that if there is clinical suspicion despite results, repeat testing or testing for metanephrines in a 24-hour urine specimen should be considered.

Test Details

New York Approved

Methodology

Mass Spectrometry

Biomarkers

Metanephrine

Analyte

Metanephrine

Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

Normetanephrine

Analyte

Normetanephrine

Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

LOINC Codes

Result Codes

40851-8 - Normetaneph Free SerPl-sCnc
25474-8 - MetanephS SerPl-sCnc
48767-8 - Annotation comment Imp

Result Turnaround Time

2-5 days

Specimen

Plasma

Volume

2 mL

Minimum Volume

1 mL

Container

Lavender (EDTA), pink (K2EDTA), or green (sodium or lithium heparin)

Collection Instructions

Centrifuge within 1 hour. Transfer to an ARUP standard transport tube and freeze immediately.

Patient Preparation

Drugs and medications may affect results and should be discontinued for at least 72 hours prior to specimen collection, if possible. Collection after 15 minutes of resting in a supine position is recommended.