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Test Code LAB4061 DEXAMETHASONE SUPPRESSION TEST

Important Note

This test may exhibit interference when sample is collcted from a person who is consuming a suppliment with a high dose of Biotin (also termed as vitamin B7, B8, Vitamin H, or coenzyme R). It is recommendfed to ask all patients who may be indicated for this test about Biotin supplementation. Patients shoul,d be cautioned to stop biotin consumptions at least 72 hours prior to the collection of the sample.

Specimen Type

Preferred Sample: Serum (SST, Gold, Corvac, Tiger, Red Top Tube)

Alternate Sample: Lithium Heparin Plasma (PST, Mint Green Tube)

 

Collection Instructions

Low Dose: Draw cortisols at 8:00 am the morning before and the morning after an 11:00 pm oral dose of 1.0 mg dexamethasone.
High Dose: Draw cortisols at 8:00 am the morning before and the morning after an 11:00 pm oral dose of 8.0 mg dexamethasone.

See also:

Cortisol Collection Job Aid

 

Specimen Volume

1 mL for each timed sample

Minimum Volume

0.2 mL for each timed sample

Turnaround Time

STAT: 1 hour
Routine: 4 hours


Times are after each specimen is drawn

Test Schedule

Daily

Sample Stability

Room Temp: 24 hours

Refrigerated: 4 days

 

Specimen Processing

Spin completely clotted SST tube for 10 minutes. Store tubes in refrigerator until testing can be done.

Method

Chemiluminescence

Reference Ranges

Cortisol Pre-Suppression ug/dL 4.3-22.4

Cortisol Post-Suppression ug/dL 

         Normal patients suppress their cortisol levels to LT 5.0 ug/dL

Critical Value: None

Reportable Limit: 0.1 - 634.0

Reporting Limit

Measuring Range: 0.1 - 63.4 ug/dL

Reporting Range: 0.1 -634.0 ug/dL (Manual Dilution 1:10 with Diluent Universal 2)

Synonyms

Cortisol Suppression (2 samples)

Test Components

Cortisol Pre-Suppression, ug/dL; Date/Time Collected; Cortisol Post-Suppression, ug/dL; Date/Time Collected.

CPT Codes

82533 × 2

Notes

Low dose dexamethasone usually does not suppress cortisol production in Cushing's Syndrome.