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Dexamethasone Suppression Test (DST), 1 Specimen : 6921
Test CodeDST1SP or 6921
Alias/See Also
Cortisol Suppression
CPT Codes
82533
Preferred Specimen
1 mL Serum
Minimum Volume
0.5 mL
Instructions
The ordering physician should administer 1 mg Dexamethasone between 11:00 p.m. and midnight. Draw serum for cortisol testing between 7:00-9:00 a.m. the next morning. Mark tube with time and date drawn.
Note: Dexamethasone not supplied by the laboratory.
Note: Dexamethasone not supplied by the laboratory.
Transport Temperature
Room temperature
Specimen Stability
Room temperature: 7 days
Refrigerated: 7 days
Frozen: 28 days
Refrigerated: 7 days
Frozen: 28 days
Methodology
Immunoassay (IA)
Setup Schedule
Monday - Saturday
Report Available
3 days (From receipt at performing laboratory)
Reference Range
For 8am Specimen:
<1.8 mcg/dL Normal Response
1.8 - 10.0 mcg/dL Equivocal
>10.0 mcg/dL High probability of Cushing's syndrome
Further diagnostic tests must be performed to confirm the diagnosis and determine etiology. Values >1.8 mcg/dL can
also be seen in endogenous depression and other forms of endogenous hypercortisolism (also known
as pseudo-Cushing) such as pregnancy, severe obesity, psychological stress, and chronic alcoholism
especially during withdrawal.
CKD: The low-dose DST can be used in patients with CKD if the post-DST morning cortisol cutoff is
adjusted for the degree of impaired kidney function.
Pregnancy: The low-dose 1 mg overnight DST is not recommended to diagnose Cushing syndrome
during pregnancy because of the risk of false-positive results.
Drugs: Drugs that induce hepatic CYP3A4 enzymes, such as barbiturates, phenytoin, rifampin, and
carbamazepine, increase the metabolism of dexamethasone and affect its level.
<1.8 mcg/dL Normal Response
1.8 - 10.0 mcg/dL Equivocal
>10.0 mcg/dL High probability of Cushing's syndrome
Further diagnostic tests must be performed to confirm the diagnosis and determine etiology. Values >1.8 mcg/dL can
also be seen in endogenous depression and other forms of endogenous hypercortisolism (also known
as pseudo-Cushing) such as pregnancy, severe obesity, psychological stress, and chronic alcoholism
especially during withdrawal.
CKD: The low-dose DST can be used in patients with CKD if the post-DST morning cortisol cutoff is
adjusted for the degree of impaired kidney function.
Pregnancy: The low-dose 1 mg overnight DST is not recommended to diagnose Cushing syndrome
during pregnancy because of the risk of false-positive results.
Drugs: Drugs that induce hepatic CYP3A4 enzymes, such as barbiturates, phenytoin, rifampin, and
carbamazepine, increase the metabolism of dexamethasone and affect its level.
Clinical Significance
Cortisol is increased in Cushing's Disease and decreased in Addison's Disease (Adrenal insufficiency).
Performing Laboratory
Quest Diagnostics
