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Test Code CORDST Cortisol DST

Methodology

Chemiluminescent/Competitive Binding Immunoenzymatic Assay

Performing Laboratory

St. Luke's Hospital Cedar Rapids

Specimen Requirements

Container/Tube:

Preferred: Green-top (heparin) tube

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

Stability: Due to possible evaporation effects, samples and calibrators on the analyzers should be analyzed/measured within 2 hours. Stable for 24 hours at 20‑25 °C, 4 days at 2‑8 °C, 12 months at ‑20 °C (± 5 °C). Freeze only once.

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

82533

Useful For

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

Report Available

STAT:  Within 1 hour of receipt

Routine:  Within 2 hours of receipt