3-Methoxytyramine, 24 Hour, Urine
Use
This test serves as a first- and second-tier screening for the diagnosis of catecholamine-secreting tumors such as pheochromocytomas and paragangliomas. It is used in conjunction with plasma tests or as an alternative for measuring catecholamine levels. It is important for identifying the presence of potentially lethal tumors that secrete excessive catecholamines.
Special Instructions
Tricyclic antidepressants, labetalol, and sotalol medications may elevate levels of catecholamines, impacting result interpretations. Patients should ideally discontinue these medications at least a week prior to collection. Urine collection involves a 24-hour duration with specific preservatives added at the beginning.
Limitations
The test is not impacted by substances that interfere with older methods. However, certain medications can affect catecholamine levels, making results difficult to interpret. The population incidence of pheochromocytomas is low, therefore excessive imaging procedures become unnecessary without distinct elevation indicators.
New York Approved
Methodology
Mass Spectrometry (LC-MS/MS)
Biomarkers
LOINC Codes
- 32618-1
- 32618-1
- 13362-9
- 3167-4
Result Turnaround Time
3-5 days
Related Documents
For more information, please review the documents below
Specimen
Urine
Volume
10 mL
Minimum Volume
3 mL
Container
Plastic urine tube
Collection Instructions
Complete a 24-hour urine collection preferably starting at the onset of a 'spell'. Add 10 g of boric acid or 25 mL of 50% acetic acid as preservative at the start of the collection.
Patient Preparation
Patients should stop certain medications as they may impact test results. Consultation with a specialist is advised for managing medication changes.
Causes for Rejection
Gross hemolysis and icterus are acceptable.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 21 days |
| Refrigerated | 28 days |
| Frozen | 28 days |