What special testing would be done to rule out pheochromocytoma (adrenal gland tumor)?

From the Guidelines

To rule out pheochromocytoma or adrenal gland tumor, I recommend starting with the measurement of circulating catecholamine metabolites, specifically plasma free or urinary fractionated metanephrines, as the initial screening test. This approach is based on the high sensitivity and specificity of these tests, as reported in the 2018 American Heart Association scientific statement on resistant hypertension 1. The measurement of plasma free metanephrines has a sensitivity of 96%−100% and specificity of 89%−98%, while urinary fractionated metanephrines have a sensitivity of 86%−97% and specificity of 86%−95% 1.

When interpreting the results, it is essential to consider the potential for false positives, particularly in patients with obesity, obstructive sleep apnea, or those taking certain medications such as tricyclic antidepressants 1. If the initial test results are elevated, clonidine-suppression testing can be used to further evaluate the results, with a specificity of 100% and sensitivity of 96% for failure to reduce plasma metanephrines by 40% 1.

Some key points to consider when ordering these tests include:

• Patients should avoid medications that can interfere with results for at least two weeks prior to testing, if possible
• Plasma metanephrines should be drawn after the patient has been resting supine for at least 30 minutes
• Imaging studies, such as computed tomography or magnetic resonance imaging, should only be pursued after biochemical evidence for a pheochromocytoma has been obtained 1

Overall, the combination of biochemical testing and anatomical imaging provides high sensitivity and specificity for diagnosis, helping to avoid the potentially dangerous consequences of an undiagnosed catecholamine-secreting tumor.

From the Research

Diagnostic Tests for Pheochromocytoma

To rule out pheochromocytoma or adrenal gland tumor, several diagnostic tests can be employed. These include:

• Biochemical tests to measure plasma free metanephrines and urinary fractionated metanephrines 2, 3, 4, 5, 6
• Radiological imaging tests such as computed tomography (CT) or magnetic resonance imaging (MRI) 2, 5
• Specific functional imaging tests like scintigraphy with (123)I-metaiodobenzylguanidine (MIBG) or positron emission tomography (PET) with (18)F-F-fluorodopamine (F-DA) 2, 5

Biochemical Tests

Biochemical tests are crucial for the diagnosis of pheochromocytoma. These tests include:

• Measuring plasma free metanephrines and urinary fractionated metanephrines 2, 3, 4, 5, 6
• Using the clonidine suppression test to differentiate between endogenous hypersecretion and false positive results in cases of moderate elevations of normetanephrine 3
• Evaluating the diagnostic performances of plasma total metanephrines alone or combined with free metanephrines and fractionated 24-h urinary metanephrines 4

Imaging Tests

Imaging tests are essential for tumor localization. These tests include:

• Computed tomography (CT) or magnetic resonance imaging (MRI) 2, 5
• Scintigraphy with (123)I-metaiodobenzylguanidine (MIBG) or (131)I-MIBG 2
• Positron emission tomography (PET) with (18)F-F-fluorodopamine (F-DA) for metastatic disease 2, 5

Additional Recommendations

Additional recommendations for patients with pheochromocytoma include:

• Performing a genetic study to identify hereditary disorders 3
• Conducting a cardiological evaluation to rule out cardiovascular involvement secondary to catecholamine hypersecretion 3
• Optimal investigation and accurate diagnosis at 'centers of excellence' with expert multidisciplinary teams 5