Clonidine Suppression Test (Four-hour)

Casandra

Casandra Test Code LC96279Version 1 (DRAFT)

Performing Lab

Lab LabcorpLab Test ID 123158CPT Code 82384

Clonidine Suppression Test (Four-hour)

Also known as: Adrenaline, Plasma, Epinephrine, Plasma, Noradrenaline, Plasma, Norepinephrine, Plasma, Plasma Catecholamines

Clinical Use

Order Test

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.

Test Details

Methodology

Mass Spectrometry

Biomarkers

Catecholamines, Total, Plasma

Analyte

Catecholamines, Total, Plasma (Baseline) • Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

Catecholamines, Total, Plasma (2 hour) • Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

Catecholamines, Total, Plasma (3 hour) • Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

Catecholamines, Total, Plasma (4 hour) • Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

Epinephrine, Plasma

Analyte

Epinephrine, Plasma (Baseline) • Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

Epinephrine, Plasma (2 hour) • Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

Epinephrine, Plasma (3 hour) • Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

Epinephrine, Plasma (4 hour) • Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

Norepinephrine, Plasma

Analyte

Norepinephrine, Plasma (Baseline) • Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

Norepinephrine, Plasma (2 hour) • Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

Norepinephrine, Plasma (3 hour) • Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

Norepinephrine, Plasma (4 hour) • Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

LOINC Codes

Order 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

Result 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

Result Turnaround Time

2-4 days

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.