Metanephrines, Fractionated, 24-Hour, Urine (Sendout)

single page view

General Information

Lab Name
Metanephrines (Fract.), URN
Lab Code
RUFMET
Epic Ordering
Metanephrines, Fractionated, 24 hr Urine (Sendout)
External Test Id
METAF
Description

Useful For:

  • A first- and second-order screening test for the presumptive diagnosis of catecholamine-secreting pheochromocytomas and paragangliomas

  • Confirming positive plasma metanephrine results

Ordering Guidance: For ruling out pheochromocytoma, the preferred screening test is Metanephrines, Fractionated, Free, Plasma [PLMET]. This test, 24 hr Urine fractionated metanephrines (RUFMET), is almost as good, but less convenient. It is commonly used as a confirmatory test to support a positive plasma free metanephrines (PLMET) result. For a recent review of the biochemical diagnosis of pheochromocytoma, see Pacak K et al. Nature Clin Pract Endocrinol Metab 2007; 3:92-102. PMID: 17237836.

Patient Preparation: Tricyclic antidepressants (TCA), labetalol, and sotalol medications may elevate levels of metanephrines producing results which cannot be interpreted. If clinically feasible, it is optimal to discontinue these medications at least 1 week before collection. For advice on assessing the risk of removing patients from these medications and alternatives, consider consultation with a specialist in endocrinology or hypertension.

Synonyms
Fractionated metanephrines-plasma, free metanephrine-plasma, MEN, MEN IIA, MEN IIB, METAF, multiple endocrine neoplasia, neuroendocrine, NMN (Normetanephrines)-plasma, paraganglioma, phaeochromocytoma, pheochromocytoma, Soft-PMET
Components

Interpretation

Method

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) Stable Isotope Dilution Analysis

Reference Range
See individual components
Ref. Range Notes

Interpretation:

Increased metanephrine and normetanephrine levels are found in patients with pheochromocytoma and tumors derived from neural crest cells.

Total urine metanephrine levels of 1300 mcg/24 hours and lower can be detected in non-pheochromocytoma hypertensive patients.

Further clinical investigation (eg, radiographic studies) is warranted in patients whose total urinary metanephrine levels are above 1300 mcg/24 hours (approximately 2 times the upper limit of normal). For patients with total urinary metanephrine levels below 1300 mcg/24 hours, further investigations may also be indicated if either the normetanephrine or the metanephrine fraction of the total metanephrines exceed their respective upper limit for hypertensive patients. Finally, repeat testing or further investigations may occasionally be indicated in patients with urinary metanephrine levels below the hypertensive cutoff, or even normal levels, if there is a very high clinical index of suspicion.

Interferences and Limitations

This test utilizes a liquid chromatography/tandem mass spectrometry method and is not affected by the interfering substances that affected the previously utilized spectrophotometric (Pisano reaction) method (ie, diatrizoate, chlorpromazine, hydrazine derivatives, imipramine, monamine oxidase [MAO] inhibitors, methyldopa, phenacetin, ephedrine, or epinephrine). This method is also not subject to the known interference of acetaminophen (seen with the plasma metanephrine high performance liquid chromatography-electrochemical method).

Ordering & Collection

Specimen Type
24-Hr Urine
Collection

Collection:

  • Prior to collection: Add 10 g (pediatric: 3 g) of boric acid or 25 mL (pediatric: 15 mL) of 50% acetic acid as preservative to an amber polyethylene 24-hr urine collection container.
    • Also accepted: Unpreserved urine refrigerated during collection.
  • Refer to Mayo Urine Preservatives-Collection and Transportation for 24-Hour Urine Specimens for additional information on acceptable collection conditions.
  • Collect urine for 24 hours. Patient should record the collection start and stop dates/times.
  • Note: The addition of preservative must occur prior to the start of the collection or application of temperature controls must occur during collection.
  • All specimens will be evaluated at Mayo Clinic Laboratories for test suitability. Samples with collection intervals <22 hours or >26 hours are not acceptable for the 24-hr test.
Handling Instructions

Outside Laboratories:

  • Mix specimen well. Measure and record total volume (required). Note the collection interval and total volume on the requisition.
  • Aliquot urine into a plastic aliquot and refrigerate.

Stability: Refrigerated (preferred): 28 days; Ambient: 28 days; Frozen: 28 days.

Quantity
requested: 10 mL urine
minimum: 3 mL urine

Processing

Processing

SPS: The addition of preservative must occur prior to the start of the collection or application of temperature controls (refrigeration) must occur during collection.

  • Mix specimen well.
  • Measure sample volume and record the total volume and collection interval on the requisition.
  • Aliquot urine into a screw-cap, plastic urine aliquot tube and refrigerate.
  • Complete the following order-at-entry questions at login/order receipt:
    • RUMETI (Metanephrine Interval)
    • RUMETV (Metanephrine Total Volume)

Sendouts:

  • Order Mayo Test: METAF.
  • Interfaced: Yes.
  • Total volume and collection interval are required for testing.

Stability: Refrigerated (preferred): 28 days; Frozen: 28 days; Ambient: 28 days.

Performance

LIS Dept Code
Sendouts Mayo Lab (RF) (MARF)
Performing Location(s)
Sendout Mayo Clinic Laboratories (Superior Drive)
800-533-1710

3050 Superior Drive NW
Rochester, MN 55901
Frequency
Performed: Monday - Friday. Report Available: 3-5 days.
Available STAT?
No

Billing & Coding

CPT codes
83835
LOINC
2608-8
Interfaced Order Code
UOW1712