Patient should discontinue taking Biotin, Vitamin B7, or Vitamin H 48 hours before getting blood drawn.
Specimen Requirements:
-OR-
1.0 mL Serum in a SST Gold Top Tube
Minimum Volume:
.25 mL Serum
Specimen Information:
Cushing’s Syndrome Method
1. A dose of 1 mg of Dexamethasone is to be given to the patient at 11:00 P.M.
2. Request an 8:00 A.M. Cortisol to be drawn the next morning.
Processing Instructions:
Must centrifuge to remove serum from cells within 24 hours of draw
Transport and Storage:
Refrigerated:5 Days
Frozen (-20 C or colder):3 Months
Clinical Interpretation
Reference Range:
0.0 - 1.8 ug/dL
Test Comments:
In the screen for Cushing’s Syndrome, the Cortisol level will not be suppressed if the disease is present.
Patients taking vitamin supplements containing high doses of biotin (>5 mg/day) may have falsely increased test results generated.
Methodology:
Chemiluminescence (CL)
Documentation
Two methods are acceptable for Dexamethasone Suppression Testing. The first one is used primarily as a screening test for Cushing’s Syndrome (Test Code DSTC1) The second is used on psychiatric patients to diagnose depression.(Test Code DST)