Free Plasma Catecholamines Test

Test Code: 084152

Synonyms:

• Adrenalin, Plasma
• Dopamine, Plasma
• Epinephrine, Plasma
• Noradrenaline, Plasma
• Norepinephrine, Plasma

Overview: This test measures the levels of catecholamines in the plasma, including adrenaline (epinephrine), noradrenaline (norepinephrine), and dopamine. These are important neurotransmitters involved in the body’s stress responses and regulation of blood pressure.

Purpose:

• Diagnosis of Pheochromocytoma and Paragangliomas: These tumors can secrete epinephrine and/or norepinephrine and may cause paroxysmal or persistent hypertension.
• Investigation of Hypertension: Especially in younger patients or in cases where hypertension is episodic, suggesting a possible pheochromocytoma.
• Comprehensive Evaluation: Often used alongside urinary metanephrines and VMA tests to diagnose pheochromocytoma, particularly when urinary collections are inconclusive.
• Neurological and Resuscitative Assessment: Helps in diagnosing disorders related to the nervous system and assessing resuscitation efforts.

Preparation:

• Dietary Restrictions: Avoid smoking for 4-6 hours and consuming walnuts, bananas, and α-methyldopa (Aldomet) for a week before the test.
• Medication Review: Discuss potential drug interactions with your doctor, as many common medications can interfere with the results.
• Pre-Test Procedure: Remain lying down in a quiet environment for at least 30 minutes before the test. An indwelling heparinized venous catheter is recommended to avoid stress from venipuncture, which can falsely elevate catecholamine levels.

Limitations:

• Sensitivity and Specificity: While elevated plasma catecholamine levels during a hypertensive episode are significant, false negatives can occur if the specimen is drawn during a symptom-free period. False positives are also common due to various factors, including environmental stress and drug interference.
• Comparison with Urinary Tests: Plasma catecholamines are generally less sensitive than urinary catecholamines for detecting certain conditions.