What if the results are negative in the 24 hour catecholamine urine test?

R/O adrenal tumor: Catecholamines are typically produced by functioing adrenal tumors causing elevated blood pressure and rapid pulse. This can be ruled out with a normal 24 hour test.

Pheochromocytoma: A negative 24 hour catecholamine test would make it very unlikely that you have a pheochromocytoma (a rare, catecholamine-secreting tumor usually benign and arising from the adrenal gland that may precipitate life-threatening hypertension).