Turnaround times
The quoted turnaround time is from sample receipt in the laboratory, to results authorisation in the Laboratory Information Management system. The times do not include transport of specimen to the laboratory or the administrative process to print and post/email reports. Service users must allow for transport and reporting time when ordering tests.
Clinical background:
Phaeochromocytoma and functional paraganglioma are rare neuroendocrine tumours that are characterised by excessive secretion of catecholamines. With such low disease prevalence, initial biochemical testing should reliably exclude or confirm the presence of a catecholamine-secreting tumour. Measurement of free (unconjugated) metanephrines in plasma has been shown to be a highly sensitive test for the detection of phaeochromocytoma. With a diagnostic sensitivity of 98% and specificity of 92%, a negative test result virtually rules out the diagnosis.
A test reference documentation is available within our resources page:
Specimen container paediatric:
Pink – EDTA
Specimen container adult:
Purple – EDTA
Minimum volume paediatric:
1 mL blood
Minimum volume adult:
1 mL blood
Special requirements:
Avoid stress.Samples viable up to 30 min from collection without ice and for 60 mins with dry ice.
Sample stability:
EDTA plasma samples are stable at -20°C to -40°C for at least 6 months.
Transport requirements:
Sample must be transported to the laboratory on dry ice within 30 mins of collection.For external laboratories, collected on dry ice and separtate within 30mins, sample must be stored and transported frozen.
Quality assurance:
RCPA Quality Assurance Program
Interpretation:
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.
Reference ranges:
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 also now included on all reports.
For a discussion of the issue of posture and relevant reference ranges please see our Plasma Metanephrines User Guide (available from link under Test Documents on this page).
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.
Other info:
Plasma metanephrine analysis is performed by HPLC-MS/MS.