Reference Range
Dopamine is a monoamine neurotransmitter that belongs to the catecholamine family; the catecholamine family includes dopamine, norepinephrine, and epinephrine. Dopamine is mainly produced in the nervous system and adrenal medulla; it plays a role in many brain functions like behavior and cognition.
The plasma reference ranges for dopamine are as follows [1] :
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Supine adults: < 10 ng/ml (conventional units); < 0.065 nmol/L (SI units)
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Ambulatory adults: < 20 ng/mL (conventional units); < 0.13 nmol/L (SI units)
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Age 3-15 years: < 60 pg/mL (conventional units); < 0.39 nmol/L (SI units)
The urinary reference range for dopamine in adults and elderly persons is 65-400 mcg/24 hr. [2]
The urinary reference ranges for dopamine in children are as follows [2] :
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0-1 year: 0-85 mcg/24 hr
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1-2 years: 10-140 mcg/24 hr
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2-4 years: 40-260 mcg/24 hr
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>4 years: 65-400 mcg/24 hr
Interpretation
Catecholamines including dopamine may be elevated in the following instances:
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After a medication withdrawal (eg, clonidine, alcohol)
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In acute illness
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With medications such as tricyclic antidepressants, buspirone, antipsychotic agents, cocaine, Levodopa, amphetamines, ephedrine, pseudoephedrine [3]
Collection and Panels
Plasma
Patient instructions are as follows:
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The patient should fast for at least 4 hours and should avoid smoking and caffeinated beverages.
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Medication that interfere with catecholamines metabolism should be avoided if possible.
Specimen collection instructions are as follows:
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An indwelling intravenous catheter should be used.
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After catheter insertion, the patient should rest for 30 minutes in the supine position.
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Withdraw the blood specimen afterward.
Collection tube - Lavender-top tube or green-top tube
Specimen preparation - Separate plasma from cells and transfer to transport tube in less than 1 hour and freeze immediately.
Storage/transport temperature - Frozen
Stability - Frozen (14 days)
Unacceptable conditions - Grossly hemolyzed specimens
Panels - Plasma fractionated catecholamines that include plasma dopamine, epinephrine, and norepinephrine
Urine
Patient instructions are as follows:
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Medication that interfere with catecholamines metabolism should be stopped at least a week prior to the urine collection if possible.
Specimen collection - 24-hour urine collection, creatinine measurement on the same urine sample to assess the specimen adequacy
Collection container - Urine container with 25 mL 6N HCl preservative.
Specimen preparation: Separate plasma from cells and transfer to transport tube in less than 1 hour and freeze immediately.
Storage/transport temperature: Refrigerate during and after collection.
Stability - Room temperature: 3 days, refrigerated: 14 days, frozen: 14 days
Unacceptable conditions - A container with pH greater than 5
Panels - Catecholamines fractionation (free), 24-hour urine including urine dopamine, epinephrine, and norepinephrine
Background
Description
Dopamine is a monoamine neurotransmitter that belongs to the catecholamine family; the catecholamine family includes dopamine, norepinephrine, and epinephrine. Dopamine is mainly produced in the nervous system and adrenal medulla; it plays a role in many brain functions like behavior and cognition. [4, 5]
Tyrosine hydroxylase converts tyrosine to 3,4-dihydroxyphenylalanine (DOPA), which is converted to dopamine under the effect of aromatic l-amino acid decarboxylase, then dopamine β-hydroxylase converts dopamine to norepinephrine and phenylethanolamine N -methyltransferase converts norepinephrine to epinephrine. [6]
Indications/Applications
Plasma and/or urine dopamine tests are indicated as part of the work up for the diagnosis of the following conditions:
Plasma and/or urine dopamine can be used in the monitoring of the following conditions:
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Neuroblastoma after therapy
Plasma fractionated catecholamines includes plasma dopamine, epinephrine, and norepinephrine, whereas 24-hour urine fractionated catecholamine includes urine dopamine, epinephrine, and norepinephrine.
In cases of pheochromocytoma, adrenal incidentaloma, and paraganglioma, plasma and urine dopamine must not be measured separately; rather, plasma fractionated catecholamines and 24-hour urine fractionated catecholamine should be ordered since rarely will pheochromocytomas and paragangliomas only secrete dopamine.
The most acceptable approach for pheochromocytoma diagnosis is to screen with 24-hour urine collection for fractionated metanephrines and catecholamines; if high clinical suspicion exists, then plasma fractionated metanephrines should then follow as a confirmatory test.
During the work-up for neuroblastoma, dopamine, whether in the urine or the plasma, should be measured in combination with 24-hour urine vanillylmandelic acid (VMA) and homovanillic acid (HVA).