Metanephrines with 3-Methoxytyramine, 24 Hour, Urine
Use
This test is primarily used as a first- and second-tier screening method for the presumptive diagnosis of catecholamine-secreting pheochromocytomas and paragangliomas. These tumors can cause excessive secretion of catecholamines, leading to severe hypertension and cardiac abnormalities. The test measures the metabolites of dopamine, epinephrine, and norepinephrine (which include metanephrine, normetanephrine, and 3-methoxytyramine) that are secreted in the urine, aiding in the diagnosis and management of conditions like pheochromocytomas, paragangliomas, and neuroblastoma.
Special Instructions
Patients should ideally discontinue tricyclic antidepressants, labetalol, and sotalol at least one week prior to specimen collection if clinically feasible to prevent elevated levels of metanephrines. The specimen should be collected over a 24-hour period to capture episodic releases, especially in cases of episodic hypertension. For such collections, a preservative like boric or acetic acid is added at the beginning of the collection period.
Limitations
The test may not detect catecholamine-secreting tumors in all cases, as 3-methoxytyramine is elevated in only a small proportion of patients. Medication interference from remaining drugs can skew results. Improper specimen collection or handling and inappropriate test selections can result in diagnostic confusion. This test is designed for use only with urine samples, as blood plasma levels are not measured in this paradigm. Despite its utility, sensitivity and specificity were not discussed in detail.
New York Approved
Methodology
Mass Spectrometry (LC-MS/MS)
Biomarkers
LOINC Codes
- 101400-0
- 104629-1
- 104631-7
- 104630-9
- 13362-9
- 3167-4
- 48767-8
- 32618-1
Result Turnaround Time
3-5 days
Related Documents
For more information, please review the documents below
Specimen
Urine
Volume
10 mL
Minimum Volume
4 mL
Container
Plastic urine tube
Collection Instructions
Complete a 24-hour urine collection, beginning at the onset of a 'spell' if possible. Add 10 g of boric acid or 25 mL of 50% acetic acid as a preservative at the start of collection.
Patient Preparation
Discontinue tricyclic antidepressants, labetalol, and sotalol at least 1 week before collection if clinically feasible.
Causes for Rejection
Gross hemolysis and gross icterus are acceptable.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 21 days |
| Refrigerated | 28 days |
| Frozen | 28 days |