Liquid chromatography/tandem mass spectrometry (LC/MS-MS)
Adults: Baseline <30 ng/dL
8:00 am following 1mg Dexamethasone the previous evening: >100 ng/dL
8:00 am following 8mg Dexamethasone (4x2mg doses) previous day: >800 ng/dL
3 - 6 days
Draw blood in a plain, red-top tube(s). Spin down within an hour of collection, and send 2 mL of serum frozen in a plastic vial. SST is acceptable, but must be aliquoted into a screw capped plastic tube.
Test sent to Mayo Clinic Laboratories