Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1072 page)

   
Normal range:
see Table 16.55.

TABLE 16–55. Normal Range for Urine Metanephrines

   Use

   Confirmation of elevated plasma catecholamine levels

   Diagnosis of pheochromocytoma and paraganglioma

   Diagnosis and follow-up of patients with neuroblastoma and related tumors

   First line of test in patients with lower suspicion of pheochromocytoma (patients with resistant hypertension, hyper adrenergic spells, incidentally discovered adrenal mass that does not have imaging characteristics consistent with pheochromocytoma).

   Interpretation

   Increases occur with catecholamine-secreting neurochromatin tumors such as pheochromocytoma, paraganglioma, and neuroblastoma.

   Limitations

   No caffeine intake should occur before or during collection. MAO inhibitors should be discontinued at least 1 week prior to beginning collection.

   Methylglucamine in x-ray contrast medium can cause false-negative test results.

   False positives can be caused by stress and drugs, which includes amphetamines and amphetamine-like compounds, appetite suppressants, bromocriptine, buspirone, caffeine, carbidopa–levodopa (Sinemet), clonidine, dexamethasone, diuretics, methyldopa (Aldomet), nose drops, propafenone (Rythmol), tricyclic antidepressants, and vasodilators. The effects of some drugs on catecholamine metabolite results may not be predictable.