Investigation Name:Metanephrines – Plasma

Pathology Laboratory:Clinical Chemistry/ Biochemistry

Requestable Seperately?Yes

Units:mmol/L

Minimum Sample Volume:1 mL

Expected Turnaround Time:21 days

Test Code:PMET

Sample Type:

Complex Reference Range:Metanephrine:
<1 year: <510 pmol/L
Adult/Children ≥1yr: <510 pmol/L

Normetanephrine:
<3 months: <2540 pmol/L
3 to <6 months: <2100 pmol/L
6 months to 1yr: <1440 pmol/L
Adult/Children ≥1yr: <1180 pmol/L

3-methoxytyramine:
<3 months: <420 pmol/L
3 to <6 months: <330 pmol/L
6 months to 1yr: <245 pmol/L
Adult/Children ≥1yr: <180 pmol/L

These reference ranges are based on a seated population. Ranges for samples taken in the supine posture are included on all reports.

Collection Conditions / Other Information:Avoid stress. Samples viable for up to 30 minutes from collection.
LABORATORY INSTRUCTIONS: Separate and freeze plasma immediately upon receipt. Transport frozen to referral laboratory.

Reference Laboratory Details:Department of Blood Sciences, Freeman Hospital, Freeman Road, Newcastle upon Tyne, NE7 7DN

Referred to Another Laboratory?Yes

Storage Requirements:EDTA plasma samples are stable at -20 °C to -40 °C for up to 6 months.

Further information:Plasma metanephrine or normetanephrine values greater than 4 times the upper reference interval are highly suggestive of the presence of phaeochromocytoma/paraganglioma.
Elevated results are reported with appropriate comments.

Factors affecting result:
Drugs can interfere analytically or pharmacodynamically with measurement of plasma or urinary metanephrines, potentially causing false positive results. The LC-MS/MS method for plasma free metanephrines is considered to be far less susceptible to analytical interference.
Many drugs are now known to increase catecholamine and metabolite concentrations, including tricyclic antideppressant’s, selective serotonin reuptake inhibitors, serotonin and noradrenaline reuptake inhibitors, α- and β- adrenergic receptor blockers, calcium channel blockers, monoamine oxidase inhibitors, Levo(L)-Dopa, methyldopa and several stimulant/sympathomimetic drugs.

Ideally patients should discontinue all medications that may affect plasma and urinary catecholamine or metanephrine concentrations prior to sampling. In practice, it is not always possible to discontinue medication before testing and it might be better to repeat testing only when initial tests are elevated.