Metanephrines, Fractionated, Free, Plasma
Use
This test is used as a screening tool for the presumptive diagnosis of catecholamine-secreting pheochromocytomas or paragangliomas. Pheochromocytoma is a rare tumor of chromaffin cells of the adrenal medulla that can cause severe episodes of hypertension. Metanephrines are 3-methoxy metabolites of epinephrine and norepinephrine, which are cosecreted with catecholamines by pheochromocytomas, making them more sensitive and specific indicators than plasma catecholamines in identifying pheochromocytoma patients.
Special Instructions
Patient preparation is crucial: use of an Epi-pen within the last 7 days may produce inaccurate results. Plasma should be aliquoted into a plastic vial within 2 hours of collection.
Limitations
While the plasma free metanephrine test has a high sensitivity for excluding pheochromocytoma, confirmatory testing using a second strategy is recommended due to the potential for false positives. Substances that increase catecholamine levels, such as MAOIs and some anesthetic gases, can result in elevated metanephrine levels. Metyrosine treatment can artifactually decrease metanephrine levels.
New York Approved
Methodology
Mass Spectrometry (LC-MS/MS)
Biomarkers
LOINC Codes
- 57772-6
- 40851-8
- 49700-8
Result Turnaround Time
2-5 days
Related Documents
For more information, please review the documents below
Specimen
Plasma
Volume
1 mL
Minimum Volume
0.3 mL
Container
Lavender top (EDTA) tube, then transfer to a plastic vial
Collection Instructions
Within 2 hours of collection centrifuge and aliquot plasma into a plastic vial.
Patient Preparation
Use of an Epi-pen within the last 7 days may produce inaccurate results.
Causes for Rejection
None noted; gross hemolysis, lipemia, or icterus acceptable
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 7 days |
| Refrigerated | 14 days |
| Frozen | 28 days |