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Test Code CORDST Cortisol DST, LAB2383


Chemiluminescent/Competitive Binding Immunoenzymatic Assay

Performing Laboratory

St. Luke's Hospital Cedar Rapids

Specimen Requirements




Preferred: Green-top (heparin) tube

Acceptable: Gold-top serum gel tube or Plain Red-top tube
Specimen Volume: 170 uL of plasma or serum

Stability: Keep tubes stoppered and upright at all times.  Do not use samples that have been stored at room temperature for longer than 8 hours.  Tightly cap and refrigerate specimens at 2° to 8°C if the assay is not completed within 8 hours.  Freeze samples at or below -20°C if the sample is not assayed within 48 hours.  Freeze samples only once and mix thoroughly after thawing.

Collection Instructions: Dexamethasone is given orally at 2300 or 2400 hours. Blood for a cortisol determination is drawn at 0800 the following morning.

Note: 1. Nursing unit must order dexamethasone from pharmacy (with dosage to be determined by physician).


Reference Values

Cortisol: ≤3.0 ug/dL (post administration of 1 mg dose)

Cortisol: <50% of baseline (post administration of 4 mg dose)

Day(s) Test Set Up

Monday through Sunday

Test Classification and CPT Coding


Useful For

The dexamethasone Suppression Test is helpful in aiding in the diagnosis of Cushing's Syndrome.