Clonidine Suppression Test (Three-hour)

CPT: 82384(x3)
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Test Details


  • Adrenaline, Plasma
  • Epinephrine, Plasma
  • Noradrenaline, Plasma
  • Norepinephrine, Plasma
  • Plasma Catecholamines

Test Includes

Catecholamines, total, plasma (base); catecholamines, total (two-hour); catecholamines, total (three-hour); epinephrine, plasma (base); epinephrine, plasma (two-hour); epinephrine, plasma (three-hour); norepinephrine, plasma (base); norepinephrine, plasma (two-hour); norepinephrine, plasma (three-hour)


Diagnose pheochromocytoma and those paragangliomas that may secrete epinephrine, norepinephrine, or both. Such tumors may cause paroxysmal or persistent hypertension. Investigation of hypertensive patients, especially younger individuals, particularly when hypertension is paroxysmal, suggesting pheochromocytoma.2


Plasma levels are useful if elevated, especially during or immediately following an episode of hypertension, but false-negatives occur when the specimen is drawn during an uneventful period. Normotensive pheochromocytoma has been reported.3 False-positive results are common. Epinephrine secretion increases in response to cold and hypoglycemia. Drugs that may affect plasma norepinephrine levels include α- and β-adrenergic blockers, vasodilators, clonidine, bromocriptine, theophylline, phenothiazine, tricyclic antidepressants, labetalol, calcium channel blockers, converting enzyme inhibitors, bromocriptine, chlorpromazine, haloperidol, and cocaine.


High-pressure liquid chromatography (HPLC) with electrochemical (EC) detection

Additional Information

Several medications have been shown to prevent clonidine suppression, thus rendering false-positive results. These include β-adrenergic blockers, tricyclic antidepressants, and thiazide diuretics. If possible, these drugs should be discontinued 48 hours before collection. The α-adrenergic blocking agents do not interfere with clonidine suppression.2 Several definitions of a normal plasma catecholamine response to clonidine have been postulated:

• A minimum plasma norepinephrine level ≤500 pg/mL4

• ≥50% norepinephrine decline from baseline and a norepinephrine level ≤500 pg/mL5

• A minimum plasma total catecholamine (norepinephrine+epinephrine) concentration ≤500 pg/mL6

Sjoberg et al have concluded that minimal suppression occurs two to three hours after clonidine administration with the greatest diagnostic accuracy (92%) obtained when the normal response is defined as a level of total plasma catecholamine ≤500 pg/mL. Taylor et al7 have demonstrated an increase in false-positive results by using the 50% reduction criteria. This is especially true if the baseline results are within the established reference interval.

Specimen Requirements


Plasma, frozen


One tube (3 mL) each for baseline specimen, two-hour specimen, and three-hour specimen

Minimum Volume

One tube (2.2 mL) each for baseline specimen, two-hour specimen, and three-hour specimen


Chilled lavender-top (EDTA) tube

Patient Preparation

The patient should fast overnight and abstain from smoking. Walnuts, bananas, and interfering medications should be avoided for a week prior to specimen collection. An indwelling heparinized catheter is recommended, as venipuncture can cause an increase in the substances for which testing is being performed. The patient should remain recumbent during the entire collection procedure. Thirty minutes after the insertion of the indwelling catheter, blood is drawn for the baseline catecholamine determination. Clonidine hydrochloride (0.3 mg) is given orally, and repeat specimens for plasma catecholamines are collected two and three hours later.1


Draw blood in chilled lavender-top (EDTA) tube. Invert tube to allow preservatives to mix thoroughly. Centrifuge at 4°C (chill carriers if a refrigerated centrifuge is unavailable). Transfer plasma to labeled plastic transport tubes. Freeze immediately at -20°C and ship frozen. “Baseline,” “two-hour,” and “three-hour” should be prelabeled on the transport tubes. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.

Storage Instructions


Causes for Rejection

Specimen not drawn in correct tube; plasma not received frozen; thawed specimen; inadequate patient preparation

Clinical Information


1. Sjoberg RJ, Simcic KJ, Kidd GS. The clonidine suppression test for pheochromocytoma. A review of Its utility and pitfalls. Arch Intern Med. 1992 Jun; 152(6):1193-1197. 1599347
2. Sheps SG, Jiang NS, Klee GG, van Heerden JA. Recent developments in the diagnosis and treatment of pheochromocytoma. Mayo Clin Proc. 1990 Jan; 65(1):88-95 (review). 1967325
3. Feldman JM, Blalock JA, Zern RT, et al. Deficiency of dopamine-β-hydroxylase: A New mechanism for normotensive pheochromocytomas. Am J Clin Pathol. 1979 Aug; 72(2):175-185. 474494
4. Bravo EL, Tarazi RC, Fouad FM, Vidt DG, Gifford RW Jr. Clonidine suppression test: A useful aid in the diagnosis of pheochromocytoma. N Engl J Med. 1981 Sep 10; 305(11):623-626. 7266587
5. Manger WM, Gifford RW, Hoffman BB. Pheochromocytoma: A clinical and experimental overview. Current Probl Cancer. 1985 May; 9(5):1-89 (review). 3021396
6. Bravo EL, Gifford RW Jr. Current concepts. Pheochromocytoma: Diagnosis, localization, and management. N Engl J Med. 1984 Nov 15; 311(20):1298-1303 (review). 6149463
7. Taylor HC, Mayes D, Anton AH. Clonidine suppression test for pheochromocytoma: Example of misleading results. J Clin Endocrinol Metab. 1986 Jul; 63(1):238-242. 3711261


Goldstein DS, Feuerstein GZ, Kopin IJ, Keiser HR. Validity of liquid chromatography with electrochemical detection for measuring dopamine in human plasma. Clin Chim Acta. 1981 Dec 9; 117(2):113-120. 7307273
Pesce AJ, Kaplan LA. Methods in clinical chemistry. St Louis, Mo: CV Mosby; 1987:948.


Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
123133 Clonidine Suppression (3-Hour) 123134 Catechol,Pl,T(2 hr) pg/mL 16558-9
123133 Clonidine Suppression (3-Hour) 123135 Epinephrine,Pl(2 hr) pg/mL 1462-1
123133 Clonidine Suppression (3-Hour) 123136 Norepineph, Pl(2 hr) pg/mL 1604-8
123133 Clonidine Suppression (3-Hour) 123137 Catechol,Pl,T(3 hr) pg/mL 16559-7
123133 Clonidine Suppression (3-Hour) 123138 Epinephrine,Pl(3 hr) pg/mL 1463-9
123133 Clonidine Suppression (3-Hour) 123139 Norepineph, Pl(3 hr) pg/mL 1605-5
123133 Clonidine Suppression (3-Hour) 123141 Catechol,Pl,T(Base) pg/mL 1388-8
123133 Clonidine Suppression (3-Hour) 123142 Epinephrine,Pl(Base) pg/mL 1464-7
123133 Clonidine Suppression (3-Hour) 123143 Norepineph, Pl(Base) pg/mL 1606-3
123133 Clonidine Suppression (3-Hour) 123350 Clonidine,Base N/A
123133 Clonidine Suppression (3-Hour) 123352 Clonidine,2hr N/A
123133 Clonidine Suppression (3-Hour) 123353 Clonidine,3hr N/A

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