Diagnostic Criteria for Pheochromocytoma

Screening and Interpretation

• When screening for pheochromocytoma, values >4 times the upper limit of normal are highly specific for the diagnosis and warrant immediate imaging, according to the American College of Physicians 1
• Values between 1-4 times the upper limit require repeat testing and potentially clonidine suppression testing, as recommended by the American College of Physicians 1

Laboratory Considerations

• Spot urine samples should be normalized to creatinine concentration to account for variations in urine concentration due to hydration status, as suggested by the American Diabetes Association 2, 3, 4
• Results should be interpreted with caution when urinary creatinine is below 2 mmol/L, as these can appear falsely elevated, according to the European Association for the Study of the Liver 5

Factors Influencing Results

• Obesity may cause false-positive elevations in spot urine metanephrines, as noted by the American College of Physicians 1
• Obstructive sleep apnea may cause false-positive elevations in spot urine metanephrines, as noted by the American College of Physicians 1
• Tricyclic antidepressant use may cause false-positive elevations in spot urine metanephrines, as noted by the American College of Physicians 1