What are the diagnostic tests, including blood and urine tests, for pheochromocytoma (adrenal gland tumor)?

From the Guidelines

Diagnosing pheochromocytoma requires blood and urine tests that measure catecholamines and their metabolites, with plasma free metanephrines and 24-hour urinary fractionated metanephrines being the most reliable initial screening tests. These tests are effective because pheochromocytomas continuously produce catecholamines (epinephrine and norepinephrine) that are metabolized to metanephrines, making these metabolites more reliable markers than the parent hormones which can fluctuate 1.

Key Considerations for Testing

• Patients should fast overnight and rest supine for 30 minutes before blood collection, avoiding medications that may interfere with results such as tricyclic antidepressants, acetaminophen, and certain antihypertensives.
• The 24-hour urine collection requires preservative and should be kept cold during collection, with dietary restrictions including avoidance of caffeine, alcohol, and vanilla-containing foods for 48 hours before testing.
• Elevated levels of metanephrines (normetanephrine and metanephrine) are highly suggestive of pheochromocytoma, with levels more than three times the upper limit of normal being particularly significant.

Next Steps After Positive Screening

If initial tests are positive, imaging studies like CT or MRI are typically performed to locate the tumor, followed by functional imaging if necessary, as recommended by guidelines 1.

Importance of Early Diagnosis

Given the high morbidity and mortality of not treating these tumors, and the fact that one-third are inherited, it is essential to consider the diagnosis in anyone referred for resistant hypertension, making timely and accurate diagnosis crucial 1.

From the Research

Diagnostic Tests for Pheochromocytoma

• Biochemical tests are used to diagnose pheochromocytoma, including measurement of plasma free metanephrines, urinary fractionated metanephrines, plasma catecholamines, urinary catecholamines, urinary total metanephrines, and urinary vanillylmandelic acid 2
• The combination of resting plasma catecholamines and urinary metanephrines has a diagnostic accuracy of 98% in both sporadic and hereditary pheochromocytomas 3
• 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 2
• Measurement of plasma free metanephrines and urinary fractionated metanephrines is recommended for biochemical diagnosis of pheochromocytoma 4

Blood and Urine Tests

• Plasma free metanephrines and urinary fractionated metanephrines are the most sensitive tests for diagnosing pheochromocytoma 4, 2
• The sensitivity of plasma free metanephrines is 99% and the specificity is 89% 2
• The sensitivity of urinary fractionated metanephrines is 97% and the specificity is 69% 2
• The combination of plasma catecholamines and urinary metanephrines can be used to diagnose pheochromocytoma, with a diagnostic accuracy of 98% 3

Diagnostic Criteria

• A proper screening for pheochromocytoma must be performed in any patient who has episodic headaches, tachycardia, and diaphoresis; family history of pheochromocytoma or multiple endocrine neoplasia; incidental suprarenal mass; paroxysms of tachyarrhythmias or hypertension; adverse cardiovascular responses to anesthetic agents; or spells occurring during exercise or straining 3
• The diagnosis of pheochromocytoma can be confirmed with biochemical testing in virtually all patients 3