Diagnose pheochromocytoma and those paragangliomas which may secrete epinephrine, norepinephrine, or both. Such tumors may cause paroxysmal or persistent hypertension. Investigation of hypertensive patients, especially younger individuals, particularly when hypertension is paroxysmal, suggesting pheochromocytoma. Plasma catecholamines with urinary metanephrines and VMA are a recommended test battery for pheochromocytoma.3 Others recommend plasma catecholamines when urinary collections are not diagnostic. Work up multiple endocrine adenomatosis, type II. Used also in diagnosis of disorders related to the nervous system and in assessment of resuscitation.4
Additional Test Information:
The adrenal medullary catecholamines (epinephrine, norepinephrine, and their precursor, dopamine) are rapidly metabolized materials with intense vasoactivity, among many other properties. They can be synthesized by extra-adrenal cells or neoplasms of the APUD system. They are pathogenic in the episodic hypertension of pheochromocytoma, and will be elevated during and immediately after such a paroxysm. However, levels may be normal during asymptomatic intervals. Urine catecholamines, metanephrines, VMA, and HVA provide additive information. A clonidine-suppression test has been described; failure to suppress plasma catecholamines with clonidine supports the diagnosis.7-9
3 mL (plasma)
Lavender-top (EDTA) tube or green-top (heparin) tube
Patient should be fasting for four or more hours without smoking. Walnuts, bananas, and α-methyldopa (Aldomet®) should be avoided for a week prior to sampling. Other drug interference may occur, including epinephrine and epinephrine-like drugs (eg, nosedrops, sinus and cough preparations, bronchodilators, appetite suppressants). Test is unreliable in subjects on levodopa or methenamine mandelate. Avoid patient stress.2 See Limitations. An indwelling heparinized venous catheter is advocated, since venipuncture can cause an increase in the substances for which testing is being done. Patient should remain supine in quiet surroundings for at least 30 minutes.
Draw blood in lavender-top (EDTA) tube or green-top (heparin) tube. Invert to mix with preservatives. Centrifuge and transfer the plasma to labeled plastic transport tube. Freeze immediately (within one hour after collection) at -20°C and ship frozen. The time between blood collection and the preparation of plasma is quite critical; if the time exceeds one hour, catecholamine values increase (when blood is kept at 4°C) or decrease (when left at 20°C).1 To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.
Freeze. After centrifugation, the plasma can be stored up to two hours at room temperature. Sample can be kept for up to two weeks at -20°C.
Specimen not drawn in correct tube; plasma not received frozen; thawed specimen; inadequate patient preparation