Catecholamines, Fractionated, Urinary Free, 24-Hour Urine

Urine (24-hour)

30 mL aliquot

4 mL aliquot (Note: This volume does not allow for repeat testing.)

Brown urine container with 30 mL 6N HCl preservative. Caution: Strong acid. May cause skin burns.

Avoid patient stress. Many drugs (reserpine and α-methyldopa, levodopa, monoamine oxidase inhibitors, and sympathomimetic amines) may interfere and should be discontinued two weeks prior to specimen collection. Nose drops, sinus and cough medicines, bronchodilators and appetite suppressants, α₂-agonists, calcium channel blockers, converting enzyme inhibitors, bromocriptine, phenothiazine, tricyclic antidepressants, α- and β-blockers, and labetalol may interfere.¹ Mandelamine® interferes, but thiazides do not. Caffeine products should be avoided before and during collection. The patient should not be subjected to hypoglycemia or exertion. Increased intracranial pressure and clonidine withdrawal can cause false-positive results.^1,2

Work up neuroblastoma; diagnose pheochromocytoma. Pheochromocytomas and occasional paragangliomas may cause persistent or paroxysmal hypertension. Work up palpitation, severe headache, diaphoresis. Urine collections are preferred to blood sampling when there is suspicion for tumor (e.g., family history of MEA II) when hypertension is not paroxysmal. Evaluate for possible multiple endocrine adenomatosis type II.

False-negatives and false-positives occur. Urine collections for metanephrines are among the best tests for pheochromocytoma.¹ Sheps et al use urinary catecholamine fractionation as confirmation, following a metanephrine test.¹ Neuroblastoma is better worked up with urinary collections for HVA and VMA. MHPG (3-methoxy-4-hydroxyphenylethylene glycol) is a major metabolite of norepinephrine in the central nervous system; it is a metabolite of some neuroblastomas.³

This test was developed and its performance characteristics determined by Labcorp. It has not been cleared or approved by the Food and Drug Administration.

Liquid chromatography/tandem mass spectrometry (LC/MS-MS)

Adults:

• Epinephrine:

− 0 to 9 years: 0−11 μg/24 hours

− 10 to 19 years: 0−18 μg/24 hours

− >19 years: 0−20 μg/24 hours

• Norepinephrine:

− 0 to 9 years: 0−59 μg/24 hours

− 10 to 19 years: 0−90 μg/24 hours

− >19 years: 0−135 μg/24 hours

• Dopamine:

− 0 to 9 years: 0−414 μg/24 hours

− 10 to 19 years: 0−575 μg/24 hours

− >19 years: 0−510 μg/24 hours

The expression “free” in free catecholamine fractionation means unconjugated. This assay is of most value for pheochromocytoma when specimen is collected during a hypertensive episode. Since a 24-hour urine collection represents a longer sampling time than a random, or symptom-directed serum sample, and because catecholamine secretion by pheochromocytomas is intermittent, the urine test may detect some cases missed by a blood level.