Clonidine Suppression Test (Four-hour)
Also known as: Adrenaline, Plasma, Epinephrine, Plasma, Noradrenaline, Plasma, Norepinephrine, Plasma, Plasma Catecholamines
Use
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
Special Instructions
Several medications prevent clonidine suppression, potentially causing false-positive results. These include β-adrenergic blockers, tricyclic antidepressants, and thiazide diuretics. Discontinuation of these drugs 48 hours prior to collection is recommended, with α-adrenergic blocking agents not interfering with clonidine suppression.
Limitations
While elevated plasma levels are clinically useful, false negatives can occur if the specimen is drawn during an uneventful period. False positives are also common due to conditions like cold and hypoglycemia. Numerous drugs affect plasma norepinephrine levels, potentially skewing results.
Methodology
Mass Spectrometry
Biomarkers
LOINC Codes
- 1606-3
- 1464-7
- 1388-8
- 1604-8
- 1462-1
- 16558-9
- 1605-5
- 1463-9
- 16559-7
- 12528-6
- 16821-1
- 12524-5
- 1606-3
- 1464-7
- 1388-8
- 1604-8
- 1462-1
- 16558-9
- 1605-5
- 1463-9
- 16559-7
- 12528-6
- 16821-1
- 12524-5
Result Turnaround Time
2-4 days
Related Documents
For more information, please review the documents below
Specimen
Plasma
Volume
One tube (3 mL) each for baseline, two-hour, three-hour, and four-hour specimens
Minimum Volume
One tube (2.2 mL) each for baseline, two-hour, three-hour, and four-hour specimens
Container
Chilled lavender-top (EDTA) tube
Collection Instructions
Draw blood in chilled lavender-top (EDTA) tube, mix thoroughly. Centrifuge at 4°C. Transfer plasma to plastic tubes. Freeze at -20°C and ship frozen. Prelabel tubes as 'baseline,' 'two-hour,' 'three-hour,' and 'four-hour.' Submit separate frozen specimens for each test requested.
Patient Preparation
Avoid smoking, walnuts, bananas, and certain medications one week before collection. Use an indwelling heparinized catheter to minimize catecholamine elevation due to venipuncture. Remain recumbent during collection. Draw baseline blood 30 minutes after catheter insertion, administer clonidine (0.3 mg) orally, collect repeat specimens two and three hours thereafter.
Storage Instructions
Freeze
Causes for Rejection
Specimen not drawn in correct tube; plasma not received frozen; thawed specimen; inadequate patient preparation