- Screening test for Pheochromocytoma
- Single blood test, good initial screen to R/O Phaeochromocytoma
- Highly sensitive (95-98)
- Specificity only (85-89%)
- Plasma catecholamine measurement poor indicator
- Levels vary episodically, can be elevated for other reasons
- Due to rare nature of phaeochromocytoma, false positive to true positive ratio is 30:1
- 24hr Urinary Metanephrines and Catecholamines
- More cumbersome than single blood test
- Gives more stable measurement over time
- Use to confirm diagnosis if plasma metanephrines raised
- Many confounding medications
- Discontinue sympathomimetics, phenoxybenzamine, acetaminophen, psychotropic drugs
- If still equivocal – Clonidine suppression test