High-pressure liquid chromatography/tandem mass spectrometry (HPLC/MS-MS)
Adults: <30 ng/dL the morning after 1mg dexamethasone dose the previous evening
140 - 295 ng/dL the morning aftr (4 x 2 mg doses) the previous day
5 - 20 days
Draw blood in a plain, red-top tube(s). Spin down and send 3 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 Medical Laboratories; performed by Esoterix Endocrinology).