What is clonidine suppression test for pheochromocytoma?

Rationale: This test has been used to diagnose pheochromocytoma and those paragangliomas that may secrete epinephrine, norepinephrine, or both. Such tumors may cause paroxysmal or persistent hypertension.

How do you test for clonidine suppression?

Clonidine suppression test

1. The patient must be relaxed and comfortable in bed.
2. A venous cannula inserted.
3. After 30 minutes (to allow patient to settle after venepuncture) a baseline specimen for plasma catecholamines is collected.
4. The patient is given 300 µg clonidine hydrochloride orally.

Which of the following results is indicative of pheochromocytoma during clonidine suppression test?

Baseline plasma norepinephrine (NE) and epinephrine (E) levels over 2000 pg/ml or failure to suppress to less than 500 pg/ml after oral clonidine have been considered diagnostic of the presence of a pheochromocytoma.

What is a positive clonidine suppression test?

Using the first criterion for diagnosis in which the clonidine suppression test is positive when the plasma noradrenaline is >2.96 nmol l–1 at 3 h gave a sensitivity of 87% (13/15 patients) and a specificity of 95% (39/41) (Figure 1).

Can clonidine be used in pheochromocytoma?

In those patients with a plasma norepinephrine of less than 2000 pg/mL, the clonidine suppression test is 92% accurate in diagnosing pheochromocytoma when the normal response to clonidine is defined as total plasma catecholamines of less than 500 pg/mL.

How accurate is a 24 hour urine test for pheochromocytoma?

The positive and negative predictive values for 24-h urine total metanephrines in the diagnosis of sporadic pheochromocytoma were 88.0% (95% CI, 83.1–93.0%) and 98.8% (95% CI, 97.8–99.4%), respectively (Table 1).

How do you confirm pheochromocytoma?

Imaging tests

1. CT scan, a specialized X-ray technology.
2. MRI , which uses radio waves and a magnetic field to produce detailed images.
3. M-iodobenzylguanidine (MIBG) imaging, a scanning technology that can detect tiny amounts of an injected radioactive compound taken up by pheochromocytomas or paragangliomas.

How is pheochromocytoma diagnosed?

These tests may include:

1. CT scan, a specialized X-ray technology.
2. MRI , which uses radio waves and a magnetic field to produce detailed images.
3. M-iodobenzylguanidine (MIBG) imaging, a scanning technology that can detect tiny amounts of an injected radioactive compound taken up by pheochromocytomas or paragangliomas.

Why does clonidine cause hypotension?

Clonidine has an alpha-antagonist effect in the posterior hypothalamus and medulla. The final response is reduced sympathetic outflow from the central nervous system (CNS), which clinically causes a decrease in arterial blood pressure.

What can mimic a pheochromocytoma?

Thyrotoxicosis, hypoglycemia, anxiety or panic attacks, hyperthyroidism, adrenal medullary hyperplasia, familial dysautonomia, and intracranial lesions may also have similar symptoms. Various tumors including neuroblastomas, ganglioneuroblastomas and ganglioneuromas may mimic pheochromocytomas/paragangliomas.

Is the clonidine suppression test for pheochromocytoma accurate?

Although it is rarely necessary for the diagnosis of pheochromocytoma, the clonidine suppression test is an accurate and safe test in a select group of patients. The clonidine suppression test for pheochromocytoma.

Can pheochromocytoma be diagnosed with a false positive test?

However, pheochromocytoma testing is often plagued by false positive results. Here we present a patient with NF1, elevated urinary metanephrine levels, and an indeterminate adrenal nodule. Clonidine suppression testing aided diagnosis and led to definitive surgical treatment that confirmed a pheochromocytoma.

What is the normal range of norepinephrine in pheochromocytoma?

Baseline plasma norepinephrine (NE) and epinephrine (E) levels over 2000 pg/ml or failure to suppress to less than 500 pg/ml after oral clonidine have been considered diagnostic of the presence of a pheochromocytoma. We found a false negative clonidine suppression test in a patient with an asymptoma …

What is a normal urine test for pheochromocytoma?

The majority of patients without a pheochromocytoma have the following 24 hours urine levels: metanephrines <400 mcg, normetanephrines <900 mcg, total metanephrines <1000 mcg, norepinephrines <170 mcg, epinephrine levels <35 mcg and dopamine levels <700 mcg. 14 15 However, false positive results remain a common and potentially expensive problem.