Metanephrine-Free Plasma Test
Metanephrine-Free Plasma Test
The plasma-free metanephrines test measures the amount of metanephrine in the blood to check if your body produces excessive catecholamine hormones, adrenaline, and noradrenaline. These hormones are secreted by the adrenal glands (located on top of the kidneys) and are essential for normal body function. They occur in varying quantities in the blood and urine and only increase during or shortly after stress situations.
However, patients with tumors inside (pheochromocytomas) or outside the adrenal glands (paragangliomas) experience an excess release of catecholamines into the blood, along with their breakdown products (metanephrine and normetanephrine). This often leads to persistent or abrupt episodes of high blood pressure and other symptoms. If left untreated, these tumors grow and spread beyond their original location, causing hypertensive crises and raising the risk of stroke, heart attack, or even death in affected patients.
Your doctor may use a plasma-free metanephrine test if they think your high blood pressure is related to the conditions of the adrenal gland. They may also request this test if you have a family history of pheochromocytoma or genetic disorders that would increase your risk for a pheochromocytoma (e.g., multiple endocrine neoplasias [MEN] types 2A or 2B, von Hippel-Lindau [VHL] disease).
What is the Free Plasma Metanephrine Test Used For?
The free plasma metanephrine test is used
To screen patients for pheochromocytoma or paraganglioma who have persistent hypertension or are currently experiencing a sudden burst (paroxysm) of hypertension
To diagnose pheochromocytoma in patients who have hypertension but not responding to treatment
For patients who have genetic risk for adrenal tumors
To monitor the recurrence of the tumor in patients who have been previously treated for phaeochromocytoma or paraganglioma
Symptoms of Pheochromocytoma
Pheochromocytoma can cause various symptoms, including
High blood pressure
Headache
Panic attack
Nausea and vomiting
Heavy sweating for no known reason
Impeding sense of doom
Nervous shaking
Shortness of breath
Pale skin
Constipation
Weight loss
Pain in the upper belly
Preparation for Test
Do not eat or drink anything except water for 8-10 hours before the test. Also, avoid consuming caffeine-containing beverages like tea, coffee, and colas, and refrain from exercising or smoking before blood collection. Additionally, inform your doctor about the medications you take, as some may interfere with the test. However, do not stop your medicines unless your doctor instructs you to do so and provides specific directions.
Interpretation of Test Results
Positive result (Abnormal)
This report suggests higher-than-normal levels of free metanephrine in the provided sample, indicating the presence of an adrenal tumor in symptomatic patients. Additional laboratory tests are recommended to confirm the diagnosis.
Elevated metanephrine levels also indicate treatment failure in patients who have been previously treated for adrenal tumors.
Negative result (Normal)
This report suggests normal metanephrine blood levels, which means it is unlikely that you have a catecholamine-producing adrenal tumor.
FAQs
When is Metanephrin free plasma test requested?
The Metanephrine free plasma test is requested under the following situations:
- When a patient is suspected of having a catecholamine-secreting tumor.
- When a patient experiences persistent or recurring symptoms indicating significantly high blood pressure.
- When a patient's high blood pressure does not respond to standard treatment.
- When an adrenal tumor is incidentally detected during an imaging test for another condition in an asymptomatic patient.
- When there is a family history of a catecholamine-secreting tumor.
- When a patient continues to exhibit symptoms of high blood pressure despite being treated for a catecholamine-secreting tumor.
What factors can affect the Metanephrine free plasma test results?
Physical stress, caffeine, alcohol, and use of certain medications, such as beta-blockers, amphetamines, chlorpromazine, buspirone, phenoxybenzamine and tricyclic antidepressants, can affect metanephrine test results. So, to confirm the original findings, the doctor may repeat the test after minimizing these influences.
What are the limitations of the Metanephrine free- plasma test?
Although the metanephrines free plasma test is highly sensitive in detecting and diagnosing catecholamine-secreting tumors, it cannot tell the doctor the location of the tumor or whether or not it's benign. Additionally, false positive results can occur due to the condition's rarity.
Is the level of plasma-free metanephrines detected proportional to the tumor size?
No, because even a very small tumor can produce large amounts of catecholamines.
Will there be any side effects of this test?
The metanephrine free plasma test has no side effects except that you might have slight pain or occasional bleeding at the needle insertion site, which will soon go away.
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