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Test Code PMET Metanephrines, Fractionated, Free, Plasma

Additional Codes

CNE Order Code: MET-Frac

Reporting Name

Metanephrines, Fract., Free, P

Useful For

Screening test for presumptive diagnosis of catecholamine-secreting pheochromocytomas or paragangliomas

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Plasma EDTA


Specimen Required


Patient Preparation: Use of an Epi-pen within the last 7 days may produce inaccurate results.

Collection Container/Tube: Lavender top (EDTA)

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions: Centrifuge and aliquot plasma into a plastic vial within 2 hours of collection.


Specimen Minimum Volume

0.3 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Plasma EDTA Frozen (preferred) 28 days
  Refrigerated  14 days
  Ambient  7 days

Reference Values

METANEPHRINE, FREE

<0.50 nmol/L

 

NORMETANEPHRINE, FREE

<0.90 nmol/L

Day(s) Performed

Monday through Saturday

CPT Code Information

83835

LOINC Code Information

Test ID Test Order Name Order LOINC Value
PMET Metanephrines, Fract., Free, P 57772-6

 

Result ID Test Result Name Result LOINC Value
10140 Normetanephrine, Free 40851-8
10139 Metanephrine, Free 49700-8

Interpretation

In the normal population, plasma metanephrine and normetanephrine levels are low, but in patients with pheochromocytoma or paragangliomas, the concentrations may be significantly elevated. This is due to the relatively long half-life of these compounds, ongoing secretion by the tumors and, to a lesser degree, peripheral conversion of tumor-secreted catecholamines into metanephrines.

 

Measurement of plasma free metanephrines appears to be the best test for excluding pheochromocytoma. The test's sensitivity approaches 100%, making it extremely unlikely that individuals with normal plasma metanephrine and normetanephrine levels suffer from pheochromocytoma or paraganglioma.(1,2)

 

Due to the low prevalence of pheochromocytomas and related tumors (<1:100,000), it is recommended to confirm elevated plasma free metanephrines with a second, different testing strategy in order to avoid large numbers of false-positive test results.(3) The recommended second-line test is measurement of fractionated 24-hour urinary metanephrines (METAF / Metanephrines, Fractionated, 24 Hour, Urine). In most cases this strategy will suffice in confirming or excluding the diagnosis. Occasionally, it will be necessary to extend this approach if there is a very high clinical index of suspicion or if test results are nonconclusive. In these cases, repeat plasma and urinary metanephrines testing, additional measurement of plasma or urinary catecholamines, or imaging procedures might be indicated.

 

Elevated results are reported with appropriate comments.

Report Available

2 to 5 days

Reject Due To

Gross hemolysis Reject
Gross lipemia OK
Gross icterus OK

Method Name

Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)

Forms

If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:

-General Request (T239)

-Oncology Test Request (T729)