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HelpTest Code 3MT 3-Methoxytyramine, 24 Hour, Urine
Reporting Name
3-Methoxytyramine, 24h, UPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Useful For
A first- and second-tier screening test for the presumptive diagnosis of catecholamine-secreting pheochromocytomas and paragangliomas
Testing in conjunction or as an alternative to plasma metanephrines (PMET / Metanephrines, Fractionated, Free, Plasma) or plasma catecholamine (CATP / Catecholamine Fractionation, Free, Plasma) testing
Method Name
Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
Necessary Information
24-Hour volume (in milliliters) is required.
Specimen Required
Patient Preparation: Tricyclic antidepressants, labetalol, and sotalol medications may elevate levels of catecholamines producing results that cannot be interpreted. If clinically feasible, it is optimal to discontinue these medications at least 1 week before collection. Levodopa (Sinemet) medication will cause false-positive results. For advice on assessing the risk of removing patients from these medications and alternatives, consider consultation with a specialist in endocrinology or hypertension.
Supplies: Urine Tubes, 10 mL (T068)
Submission Container/Tube: Plastic urine tube
Specimen Volume: 10 mL
Collection Instructions:
1. Complete 24-hour urine collections are preferred, especially for patients with episodic hypertension; ideally the collection should begin at the onset of a "spell."
2. Add 10 g (pediatric: 3 g) of boric acid or 25 mL (pediatric: 15 mL) of 50% acetic acid as preservative at start of collection.
3.Collect urine for 24 hours..Â
Additional Information: See Urine Preservatives-Collection and Transportation for 24-Hour Urine Specimens for multiple collections.
Specimen Type
UrineSpecimen Minimum Volume
3 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Urine | Refrigerated (preferred) | 28 days | |
| Frozen | 28 days | ||
| Ambient | 21 days |
Reject Due To
| Gross hemolysis | OK |
| Gross icterus | OK |
Reference Values
Males: ≤306 mcg/24 h
Females: ≤242 mcg/24 h
For International System of Units (SI) conversion for Reference Values, see www.mayocliniclabs.com/order-tests/si-unit-conversion.html
Interpretation
Further clinical investigation (eg, radiographic studies) and genetic studies might be warranted in patients whose 3-methoxytyramine (3MT), metanephrine, or normetanephrine are elevated or when there is a very high clinical index of suspicion.
Increased 3MT levels are found in patients with pheochromocytoma and dopamine-secreting tumors.
3MT levels of 306 mcg/24 h or less in male patients and 242 mcg/24 h or less in female patients can be detected in non-pheochromocytoma hypertensive patients.
Day(s) Performed
Monday through Friday
Report Available
3 to 5 daysTest Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
82542
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| 3MT | 3-Methoxytyramine, 24h, U | 32618-1 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 65157 | 3-Methoxytyramine, U | 32618-1 |
| TM120 | Collection Duration (h) | 13362-9 |
| VL120 | Volume (mL) | 3167-4 |