Metanephrines, Plasma (Free)
Also known as: META PF
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
Drugs and medications may affect results and should be discontinued for at least 72 hours prior to specimen collection, if possible. Collection of the specimen after the patient has rested for 15 minutes in a supine position is recommended. If test results are inconsistent with clinical evidence, drug interference should be considered, and if appropriate, the patient should discontinue the potential interferent for 48-72 hours and a new sample collected for retesting.
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.
New York Approved
Methodology
Mass Spectrometry
Biomarkers
LOINC Codes
- 40851-8
- 25474-8
- 48767-8
Result Turnaround Time
2-5 days
Related Documents
For more information, please review the documents below
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.
Storage Instructions
Frozen. Separate specimens must be submitted when multiple tests are ordered.
Causes for Rejection
Plasma separator tubes, body fluids other than EDTA or heparinized plasma, grossly hemolyzed samples.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | Unacceptable |
| Refrigerated | 10 Days |
| Frozen | 1 month |