Catecholamine testing is primarily used to help detect and rule out pheochromocytomas in symptomatic patients. It also may be ordered to help monitor the effectiveness of treatment when a pheochromocytoma is discovered and removed and to monitor for recurrence. The plasma test is most useful when the patient has persistent hypertension or is currently experiencing an episode of hypertension. This is because the hormones do not linger in the blood; they are used by the body, metabolized, and/or excreted. Urine catecholamine testing measures the total amount of catecholamines released in 24 hours. Since the hormone levels may fluctuate significantly during this period, the urine test may detect excess production that is missed with the blood test. Plasma and urine tests may be ordered together or separately and/or along with urine and/or plasma metanephrines to look for excessive amounts of both catecholamines and their metabolites.

Since these tests are affected by drugs, foods, and stresses, there will be a certain number of false positives. For this reason, catecholamine testing is not recommended as a screen for the general public. Doctors will frequently investigate a positive result by evaluating a patient’s stresses and intake, work to alter or minimize any influences, and then repeat the test to confirm the original findings.

Occasionally, the tests may be ordered on an asymptomatic person if an adrenal or neuroendocrine tumor is detected during a scan that is done for another purpose or if the patient has a strong personal or family history of pheochromocytomas (as they may recur and there is a genetic link in some cases).

Catecholamine testing is ordered when a doctor either suspects that a patient has a pheochromocytoma or wants to rule out the possibility. He may order it when a patient has persistent or recurring hypertension along with symptoms such as headaches, sweating, flushing, and rapid heart rate. It may also be ordered when a patient has hypertension that is not responding to treatment (patients with a pheochromocytoma are frequently resistant to conventional therapies).

Occasionally, the test may be ordered when an adrenal tumor is detected incidentally or when a patient has a family history of pheochromocytomas. It may also be used as a monitoring tool when a patient has been treated for a previous pheochromocytoma.

Since the catecholamine test is sensitive to many outside influences and pheochromocytomas are rare, a doctor may see more false positives with this test than true positives. If a symptomatic patient has large amounts of catecholamines in her blood and/or urine, further investigation is indicated. Serious illnesses and stresses can cause moderate to large temporary increases in catecholamine levels. Doctors must evaluate the patient as a whole - his physical condition, emotional state, medications, and diet. When interfering substances and/or conditions are found and resolved, the doctor will frequently re-test the patient to determine whether the catecholamines are still elevated. The doctor may also order blood and/or urine metanephrine testing to help confirm his findings and imaging tests (such as an MRI) to help find the tumor(s).

If levels are elevated in a patient who has had a previous pheochromocytoma, then it is likely that either treatment was not fully effective or that the tumor is recurring.

If the concentrations of catecholamines are normal in both the plasma and urine, then it is unlikely that a patient has a pheochromocytoma. Pheochromocytomas do not necessarily produce catecholamines at a constant rate, however. If the patient has not had a recent paroxysm of hypertension, their plasma and urine concentrations of catecholamines could be at normal or near normal levels even when a pheochromocytoma is present.

While plasma and urine catecholamine testing can help detect and diagnose pheochromocytomas, they cannot tell the doctor where the tumor is, whether there is more than one, or whether or not the tumor is benign (although most are). The amount of catecholamines produced does not necessarily correspond to the size of the tumor. This is a physical characteristic of the tumor tissue. The total amount of catecholamines produced will tend to increase, however, as the tumor increases in size.

It is very important to talk to your doctor before discontinuing any prescribed medications. He will work with you to identify interfering substances and drug treatments to determine which of them can be safely interrupted and which must be continued for your well-being. Some of the substances that can interfere with catecholamine testing include: acetaminophen, aminophylline, amphetamines, appetite suppressants, coffee, tea, and other forms of caffeine, chloral hydrate, clonidine, dexamethasone, diuretics, epinephrine, ethanol (alcohol), insulin, imipramine, lithium, methyldopa (Aldomet), MAO (monoamine oxidase) inhibitors, nicotine, nitroglycerine, nose drops, propafenone (Rythmol), reserpine, salicylates, theophylline, tetracycline, tricyclic antidepressants, and vasodilators. The effects of these drugs on catecholamine results will be different from patient to patient and are often not predictable.