Plasma free metanephrine

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Also known as: Plasma metanephrine
Formal name: Fractionated plasma free metanephrines (normetanephrine and metanephrine)

At a Glance

Why Get Tested?

To help diagnose or rule out a phaeochromocytoma

When to Get Tested?

If you have symptoms of persistent or episodic high blood pressure such as severe headaches, rapid heart rate and sweating

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

Pre-sample preparation is important for accurate results. You should discontinue adrenaline and adrenaline-like drugs for at least 1 week before the test, stop using paracetamol (acetaminophen) 48 hours before, and fast for 8 - 10 hours prior to collection. It is especially important not to have any caffeine containing food (soft drinks, chocolate), coffee (including decaffeinated), tobacco, tea, or alcohol for at least 4 hours before specimen collection.

The Test Sample

What is being tested?

The plasma free metanephrines test measures the amount of metanephrine and normetanephrine in the blood. These substances are metabolitesof adrenaline and noradrenaline. Adrenaline and noradrenaline are catecholamine hormones that help regulate the flow and pressure of blood throughout the body and play important roles in the body’s response to stress. They are produced in the medulla (interior) of the adrenal glands. Each person has two adrenal glands and they are small, triangular organs located on top of the kidneys. The catecholamines that the adrenal glands create, and their metabolites (metanephrine and normetanephrine), are normally found in small fluctuating quantities in both the blood and urine.

A rare tumour called a phaeochromocytoma can produce large amounts of catecholamines, resulting in significantly increased concentrations of metanephrine and normetanephrine in both the blood and urine. About 90% of phaeochromocytomas form in the adrenal glands and, while a few are cancerous, most are benign – they do not spread beyond their original location - although most do continue to grow.

The catecholamines that phaeochromocytomas produce can cause persistent hypertension (high blood pressure) and/or paroxysms (bouts) of severe high blood pressure. This can cause symptoms such as headaches, palpitations, sweating, nausea, anxiety, and tingling in the extremities. Left untreated, the symptoms may worsen as the phaeochromocytoma grows and, over a period of time, the high blood pressure that the tumour causes may damage body organs such as the kidneys and heart and raise the risk of an affected patient having a stroke or heart attack.

Plasma free metanephrines and urine catecholamines can be used to detect the presence of phaeochromocytomas. It is important to diagnose and treat these rare tumours because they cause a potentially curable form of high blood pressure. In most cases, the tumours can be surgically removed and/or treated to significantly reduce the amount of catecholamines being produced and to reduce or eliminate their associated symptoms and complications.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in your arm. There is some variation between laboratories in the specifics of how the sample is collected. At the collection site, you may be asked to lie down and rest quietly for 15 – 30 minutes prior to sample collection, and your blood may be collected while you are lying down. In other circumstances, you may just be seated upright with little or no rest time before the sample collection.

Is any test preparation needed to ensure the quality of the sample?

Pre-sample preparation is important for accurate results. You should discontinue adrenaline and adrenaline-like drugs for at least 1 week before the test, stop using paracetamol (acetaminophen) 48 hours before, and fast for 8 - 10 hours prior to collection. It is especially important not to have any caffeine containing food (soft drinks, chocolate), coffee (including decaffeinated), tobacco, tea, or alcohol for at least 4 hours before specimen collection.

The Test

Common Questions

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.