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:
Clinical utility
Metanephrines are measured in plasma for the biochemical diagnosis and monitoring of phaeochromocytoma and functional paraganglioma.
Clinical significance
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.
Specimen container paediatric:
Plasma, Pink – EDTA
Specimen container adult:
Plasma, Purple – EDTA
Minimum volume paediatric:
1 mL blood
Minimum volume adult:
1 mL blood
Sample stability:
Plasma samples are stable at -20°C to -40°C for at least 6 months.
Transport requirements:
- Transport to laboratory immediately
- Blood sample must be transported to the laboratory within 30 mins of collection at ambient temperature or within 60 mins on ice.
- For external laboratories
- after separation of plasma, the sample must be stored and transported frozen.
Freq Analysis:
2-3 x weekly
Quality assurance:
UK NEQAS
Interpretation:
Plasma metanephrine or normetanephrine values greater than 3 times the upper reference interval are highly suggestive of the presence of phaeochromocytoma/paraganglioma.
Reference ranges:
| Age | Metanephrine (pmol/L) | Normetanephrine (pmol/L) | 3-methoxytyramine (pmol/L) |
| <3 months | <510 | <2540 | <420 |
| 3 to <6 months | <510 | <2100 | <330 |
| 6 months to 1 year | <510 | <1440 | <245 |
| >1 year, Adults | <510 | <1180 | <180 |
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
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 metanephrines analysis is performed by LC-MS/MS.