Biochemical diagnosis of pheochromocytoma: how to distinguish true- from false-positive test results.

Measurements of plasma normetanephrine and metanephrine provide a highly sensitive test for diagnosis of pheochromocytoma, but false-positive results remain a problem. We therefore assessed medication-associated false-positive results and use of supplementary tests, including plasma normetanephrine responses to clonidine, to distinguish true- from false-positive results. The study included 208 patients with pheochromocytoma and 648 patients in whom pheochromocytoma was excluded.

Biochemical diagnosis of pheochromocytoma: which test is best?

Context: Diagnosis of pheochromocytoma depends on biochemical evidence of catecholamine production by the tumor. However, the best test to establish the diagnosis has not been determined.

Objective: To determine the biochemical test or combination of tests that provides the best method for diagnosis of pheochromocytoma.