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Test ID METAR Metanephrines, Fractionated, Random, Urine

Reporting Name

Metanephrines, Fract., Random, U

Useful For

A second-order screening test for the presumptive diagnosis of pheochromocytoma in patients with nonepisodic hypertension

 

Confirming positive plasma metanephrine results in patients with nonepisodic hypertension

Profile Information

Test ID Reporting Name Available Separately Always Performed
RCTU Creatinine Conc No Yes
METAU Metanephrines, Fractionated, U No Yes

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Urine


Specimen Required


Supplies: Urine Tubes, 10 mL (T068)

Patient Preparation: Tricyclic antidepressants and labetalol and sotalol (beta blockers) may elevate levels of metanephrines. If clinically feasible, these medications should be discontinued at least 1 week before collection.

Collection Container/Tube: Clean, plastic urine collection container

Submission Container/Tube: Plastic urine tube (T068)

Specimen Volume: 5 mL

Collection Instructions:

1. Collect a random urine specimen.

2. No preservative.


Specimen Minimum Volume

3 mL

Specimen Stability Information

Specimen Type Temperature Time
Urine Frozen (preferred) 14 days
  Ambient  7 days
  Refrigerated  7 days

Reference Values

METANEPHRINE/CREATININE

Normotensives

0-2 years: 82-418 mcg/g creatinine

3-8 years: 65-332 mcg/g creatinine

9-12 years: 41-209 mcg/g creatinine

13-17 years: 30-154 mcg/g creatinine

≥18 years: 29-158 mcg/g creatinine

 

NORMETANEPHRINE/CREATININE

Males

Normotensives

0-2 years: 121-946 mcg/g creatinine

3-8 years: 92-718 mcg/g creatinine

9-12 years: 53-413 mcg/g creatinine

13-17 years: 37-286 mcg/g creatinine

18-29 years: 53-190 mcg/g creatinine

30-39 years: 60-216 mcg/g creatinine

40-49 years: 69-247 mcg/g creatinine

50-59 years: 78-282 mcg/g creatinine

60-69 years: 89-322 mcg/g creatinine

≥70 years: 102-367 mcg/g creatinine

Females

Normotensives

0-2 years: 121-946 mcg/g creatinine

3-8 years: 92-718 mcg/g creatinine

9-12 years: 53-413 mcg/g creatinine

13-17 years: 37-286 mcg/g creatinine

18-29 years: 81-330 mcg/g creatinine

30-39 years: 93-379 mcg/g creatinine

40-49 years: 107-436 mcg/g creatinine

50-59 years: 122-500 mcg/g creatinine

60-69 years: 141-574 mcg/g creatinine

≥70 years: 161-659 mcg/g creatinine

 

TOTAL METANEPHRINE/CREATININE

Males

Normotensives

0-2 years: 241-1,272 mcg/g creatinine

3-8 years: 186-980 mcg/g creatinine

9-12 years: 110-582 mcg/g creatinine

13-17 years: 78-412 mcg/g creatinine

18-29 years: 96-286 mcg/g creatinine

30-39 years: 106-316 mcg/g creatinine

40-49 years: 117-349 mcg/g creatinine

50-59 years: 130-386 mcg/g creatinine

60-69 years: 143-427 mcg/g creatinine

≥70 years: 159-472 mcg/g creatinine

Females

Normotensives

0-2 years: 241-1,272 mcg/g creatinine

3-8 years: 186-980 mcg/g creatinine

9-12 years: 110-582 mcg/g creatinine

13-17 years: 78-412 mcg/g creatinine

18-29 years: 131-467 mcg/g creatinine

30-39 years: 147-523 mcg/g creatinine

40-49 years: 164-585 mcg/g creatinine

50-59 years: 184-655 mcg/g creatinine

60-69 years: 206-733 mcg/g creatinine

≥70 years: 230-821 mcg/g creatinine

Day(s) and Time(s) Performed

Monday through Friday; 4 p.m.

Test Classification

This test was developed and its performance characteristics determined by Laboratory Medicine and Pathology, Mayo Clinic. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

83835

LOINC Code Information

Test ID Test Order Name Order LOINC Value
METAR Metanephrines, Fract., Random, U In Process

 

Result ID Test Result Name Result LOINC Value
21546 Metanephrine/Creatinine 35644-4
RCTU Creatinine Conc 2161-8
21547 Normetanephrine/Creatinine 44342-4
21548 Total Metanephrine/Creatinine 32655-3

Clinical Information

Pheochromocytoma is a rare, though potentially lethal, tumor of chromaffin cells of the adrenal medulla that produces episodes of hypertension with palpitations, severe headaches, and sweating ("spells").

 

Pheochromocytomas and other tumors derived from neural crest cells (eg, paragangliomas and neuroblastomas) secrete catecholamines (epinephrine and norepinephrine).

 

Metanephrine and normetanephrine are the 3-methoxy metabolites of epinephrine and norepinephrine, respectively. Metanephrine and normetanephrine are both further metabolized to vanillylmandelic acid.

 

Pheochromocytoma cells also have the ability to oxymethylate catecholamines into metanephrines that are secreted into circulation.

 

While screening for pheochromocytoma is best accomplished by measuring plasma free fractionated metanephrines (a more sensitive assay), follow-up testing with urinary fractionated metanephrines (a more specific assay) may identify false-positives. Twenty-four hour urine collections are preferred, especially for patients with episodic hypertension; ideally the collection should begin at the onset of a "spell."

Interpretation

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

 

Increased urine metanephrines can be detected in nonpheochromocytoma hypertensive patients; quantification may help distinguish these patients from those with tumor-induced symptoms.

Cautions

This test utilizes a high-performance liquid chromatography (HPLC)/tandem mass spectrometry (MS/MS) method and is not affected by the interfering substances that affected the previously utilized spectrophotometric (Pisano reaction) method (ie, diatrizoate, chlorpromazine, hydrazine derivatives, imipramine, MAO inhibitors, methyldopa, phenacetin, ephedrine, or epinephrine).

 

This method is also not subject to the known interference of acetaminophen (seen with the plasma metanephrine HPLC-EC method)

 

When N-acetylcysteine is administered at levels sufficient to act as an antidote for the treatment of acetaminophen overdose, it may lead to falsely decreased creatinine results.         

Clinical Reference

1. Ito Y, Obara T, Okamoto T, et al: Efficacy of single-voided urine metanephrine and normetanephrine assay for diagnosing pheochromocytoma. World J Surg 1998;22:684-688

2. Hernandez FC, Sanchez M, Alvarez A, et al: A five-year report on experience in the detection of pheochromocytoma. Clin Biochem 2000;33:649-655

3. Pacak K, Linehan WM, Eisenhofer G, et al: Recent advances in genetics, diagnosis, localization, and treatment of pheochromocytoma. Ann Intern Med 2001;134:315-329

4. Sawka AM, Singh RJ, Young WF Jr: False positive biochemical testing for pheochromocytoma caused by surreptitious catecholamine addition to urine. Endocrinologist 2001;11:421-423

Analytic Time

3 days (not reported on Sundays)

Reject Due To

Hemolysis

NA

Lipemia

NA

Icterus

NA

Other

NA

NY State Approved

Yes

Method Name

RCTU: Enzymatic Colorimetric Assay

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