Adults
: 24 hr urine is required.
Acidified is preferred - urine is collected into acid bottles (20mL of 6mol/L HCl).
Or, if unacidified, must arrive at the laboratory within 48 hours of commencement of collection for acidification by the laboratory.
Urine catecholamines are not usually performed on adult samples except by special arrangement, however, if measurement of catecholamines is also required on the same specimen, the 24h urine MUST be collected into a plastic 2litre bottle containing acid (20 mL of 6mol/L HCl). Unlike metanephrines, acidification after collection does not suffice.
Children : Casual urine sample. Minimum sample 2 mls
Casual paediatric specimens must be acidified within 2 hours of collection.
For casual collects on children at ACH the following protocol is used:
Once the sample is collected, send immediately to the laboratory. Please mark request form "Urgent" so that samples are treated with HCl as soon as possible.
|
| Metanephrine reference ranges |
UoM:
Metanephrine 12%
Normetanephrine 12%
Principle : High performance liquid chromatography with electrochemical detection (HPLC-EC)
Urine and plasma metanephrines are the best tests for diagnosing phaeochromocytoma and paraganglioma; their performance is superior to urine catecholamines.
For diagnosing neuroblastoma , request urine HVA and catecholamines.
Effects of drugs
Some antihypertensive and other drugs cause increased metanephrines as indicated in the table, which applies to both urine and plasma metanephrines.
A drug washout period of at least 2 weeks is recommended before re-testing.
|
Drug |
met |
normet |
|
tricyclic antidepressants |
- |
+++ |
| venlafaxine | ? |
++++ |
|
phenoxybenzamine |
- |
+++ |
|
beta-blockers |
+ |
+ |
|
MAOIs (monoamine oxidase inhibitors) |
+++ |
+++ |
|
amphetamines & sympathomimetics (e.g pseudoephedrine) |
++ |
++ |
|
alpha-blockers (prazosin, doxazosin), calcium channel blockers, ACEIs, ARBs, diuretics |
- |
- |
Effects of stress or acute illness:
Metanephrines are metabolites of catecholamines, and their secretion is increased by stress e.g. acute illness, surgery, cardiac failure, stroke. Screening for phaeochromocytoma / paraganglioma should be delayed until the acute episode has settled.
a. Urinary 3-methoxytyramine may be useful in:
- Patients with a high risk of developing phaeochromocytoma and paraganglioma. Examples include established family/genetic history or histologically proven disease. Note: In adults, an isolated 3-methoxytyramine secreting tumour is rare and evidence for routine 3- methoxytyramine testing in phaeochromocytoma and paraganglioma is limited at this stage. 1
- In children and adults less than the age of 21, urinary 3-methoxytyramine has been shown to be helpful in the diagnosis and monitoring of neuroblastic disease.
- Patients with suspicion of metastatic head neck paraganglioma. Preliminary evidence suggests 3MTY may be raised in a minority of patients where metanephrine and normetanephrine may be within reference limits.
b. LabPlus report urinary 3-methoxytyramine under the following circumstances:
- 0 - < 21 years old: Routinely reported as the recommended test for neuroblastic disease.
- 2 1 or older: Reported when specifically requested and where urine metanephrines are also requested or have previously been performed.
c. Causes of false positives:
- Catecholamine rich diets including a diet containing pineapples, bananas, avocado, kiwi fruits, nuts or walnuts may increase casual urine methoxytyramine on average 2 times. This effect may last for 24 hours. 5
- Use of L-DOPA and dopamine infusion may significantly increase methoxytyramine, usually this rise is greater than 10 times the upper reference limit.
- As with metanephrine and normetanephrine, significant illness may also increase the levels of methoxytyramine to 2-4 times upper reference limit.
References:
1. Willemsen JJ, Ross HA, Wolthers BG et al. Evaluation of specific high-performance liquid-chromatographic determinations of urinary metanephrine and normetanephrine by comparison with isotope dilution mass spectrometry. Ann Clin Biochem. 2001;38:722-730
2. Pussard E, Neveux M, Guigueno N. Reference intervals for urinary catecholamines and metabolites from birth to adulthood. Clin Biochem. 2009;42:536-539.
3. Eisenhofer G, Goldstein DS, Walther MM et al. Biochemical diagnosis of pheochromocytoma: how to distinguish true- from false-positive test results. J Clin Endocrinol Metab. 2003;88:2656-2666
4. Neary, N. M., K. S. King, et al. (2011). "Drugs and pheochromocytoma--don't be fooled by every elevated metanephrine." N Engl J Med 364 (23): 2268-2270.
Emails to chemicalpathologist@adhb.govt.nz will receive priority attention from the on-call chemical pathologist.
If the query concerns a specific patient please include the NHI number in your email.
If email is not a suitable option, please contact the on-call chemical pathologist via Lablink (Auckland City Hospital ext. 22000 or 09-3078995).
Individual chemical pathologists may be contacted but will not be available at all times.
After-hours : contact Lablink (Auckland City Hospital ext. 22000 or 09-3078995) or hospital operator for on duty staff after hours.
Dr Samarina Musaad (Clinical Lead) : SamarinaM@adhb.govt.nz ext. 22402
Dr Cam Kyle: CampbellK@adhb.govt.nz ext 22052
Dr Weldon Chiu: WeldonC@adhb.govt.nz ext. 23427
Dr Campbell Heron: CHeron@adhb.govt.nz ext. 23427
Dr Sakunthala Jayasinghe: Sakunthala@adhb.govt.nz ext. 23427
ADULT:
24 hour urine collects must be either collected into acid bottles or acidified within 48 hours of commencing collection. 20 mL of 6 mol/L HCl is required per 2 L of urine. Please acidify before transporting to LabPlus.
Minimum sample aliquot 5mL.
CHILDREN:
Casual collects must be acidified within 2 hours of collection. Please acidify before transporting to LabPlus.
A pH of 2-3 is required. Minimum sample 2mL.