Pheochromocytoma: pitfalls in the biochemical evaluation.

The current work-up of a patient suspected to have a pheochromocytoma starts with the measurement of plasma or urine metanephrines. Notably, up to a quarter of these patients will have a false positive result. When the plasma or urine metanephrines are less than the 4-fold upper limit of normal, clinicians struggle between the fear of missing a potentially fatal condition and ordering costly follow up tests. In many cases, ordering unnecessary imaging studies may only increase the level of patient anxiety. This article will review various physiologic factors, pathologic conditions and medications that may influence the levels of catecholamines and their metabolites yielding false positive or false negative results. Acquiring familiarity with these conditions as well as interfering medications will equip clinicians with better interpretation skills of the biochemical tests.