Catecholamines, Fractionated, Urinary Free, Random Urine

Urine (random)

10 mL aliquot

4 mL aliquot

Use random urine transport tube containing 6N HCl or urine Monovette® with pH stabilizer (LabCorp N° 56015). Monovette® instructions accompany units. Preservative must be added to the container prior to the start of the collection. If collecting without Monovette®, use plastic urine container and adjust urine pH to <5 with 6N HCI. Caution: Strong acid. May cause skin burns.

Avoid patient stress. Many drugs (reserpine and alpha 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. Evaluate for possible multiple endocrine adenomatosis type II.

False-negatives and false-positives occur. 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 24-hour urine test may detect some cases missed by a blood or random urine level.

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)

Pediatric³ and adults:

• Epinephrine:

− 0 to 9 years: 0−37 μg/g creatinine

− 10 to 19 years: 0−17 μg/g creatinine

− >19 years: 0−19 μg/g creatinine

• Norepinephrine:

− 0 to 9 years: 0−150 μg/g creatinine

− 10 to 19 years: 0−67 μg/g creatinine

− >19 years: 0−111 μg/g creatinine

• Dopamine:

− 0 to 9 years: <1488 μg/g creatinine

− 10 to 19 years: <354 μg/g creatinine

− >19 years: <348 μg/g creatinine

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.