Biochemical Diagnosis of Pheochromocytoma: Which Test is Best? (Toward Optimal Laboratory Use)

Measuring the amount of plasma free metanephrines appears to be the best diagnostic test for identifying patients who have an adrenal gland tumor called a pheochromocytoma. This was the conclusion of researchers who measured plasma free metanephrines, plasma catecholamines, urinary catecholamines, urinary total and fractionated metanephrines, and urinary vanillylmandelic acid in a study of 858 patients.
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. Design, Setting, and Participants Multicenter cohort study of patients tested for pheochromocytoma at 4 referral centers between 1994 and 2001. The analysis included 214 patients in whom the diagnosis of pheochromocytoma was confirmed and 644 patients who were determined to not have the tumor. Main Outcome Measures Test sensitivity and specificity, receiver operating characteristic curves, and positive and negative predictive values at different pretest prevalences using plasma free metanephrines, plasma catecholamines, urinary catecholamines, urinary total and fractionated metanephrines, and urinary vanillylmandelic acid. Results Sensitivities of plasma free metanephrines (99% [95% confidence interval (CI), 96%-100%]) and urinary fractionated metanephrines (97% [95% CI, 92%-99%]) were higher than those for plasma catecholamines (84% [95% CI, 78%-89%]), urinary catecholamines (86% [95% CI, 80%-91 %]), urinary total metanephrines (77% [95% CI, 68%-85%]), and urinary vanillylmandelic acid (64% 1195% CI, 55%-71 %]). Specificity was highest for urinary vanillylmandelic acid (95% [95% CI, 93%-97%]) and urinary total metanephrines (93% [95% CI, 89%-97%]); intermediate for plasma free metanephrines (89% [95% CI, 87%-92%]), urinary catecholamines (88% [95% Cl, 85%91%]), and plasma catecholamines (81 % [95% CI, 78%-84%]); and lowest for urinary fractionated metanephrines (69% [95% Cl, 64%-72%]). Sensitivity and specificity values at different upper reference limits were highest for plasma free metanephrines using receiver operating characteristic curves. Combining different tests did not improve the diagnostic yield beyond that of a sin gle test of plasma free metanephrines. Conclusion Plasma free metanephrines provide the best test for excluding or confirming pheochromocytoma and should be the test of first choice for diagnosis of the tumor.