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.

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.

1. Sheps SG, Jiang N-S, Klee GG, et al. Recent developments in the diagnosis and treatment of pheochromocytoma. Mayo Clin Proc. 1990; 65(1):88-95. PubMed 1967325

2. Landsberg L, Young JB. Pheochromocytoma. In: Braunwald E, Isselbacher KJ, Petersdorf RG, et al, eds. Harrison's Principles of Internal Medicine. New York, NY: McGraw-Hill Information Services Co;1987:1775-1778.

3. Soldin SJ, Lam G, Pollard A, et al. High performance liquid chromatographic analysis of urinary catecholamines employing amperometric detection: Reference values and use in laboratory diagnosis of neural crest tumors. Clin Biochem. 1980; 13(6):285-291. PubMed 7214697

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