plasma metanephrines
Blood test measuring catecholamine metabolites, the preferred screening method for pheochromocytoma and paraganglioma diagnosis.
Full Definition
Plasma metanephrines represent the most sensitive and specific biochemical test for detecting catecholamine-secreting tumors. These metabolites of epinephrine (metanephrine) and norepinephrine (normetanephrine) are produced continuously within chromaffin cells, providing a more stable measurement than the parent catecholamines. The test should be performed under standardized conditions with the patient supine for at least 20 minutes, avoiding medications and conditions that can cause false elevations. Values exceeding four times the upper reference limit strongly suggest pheochromocytoma or paraganglioma.
Usage
Usage note: Document patient position, medications, and clinical context as these factors significantly affect interpretation.
In Context
- "Plasma metanephrines were markedly elevated at 15 times the upper reference limit, confirming the suspected diagnosis." — Laboratory results interpretation
- "The patient was instructed to discontinue tricyclic antidepressants before repeat plasma metanephrines testing." — Pre-test preparation instructions