0.5 mL serum in red top or serum separator tube for baseline sample (labeled PRE) and 0.5 serum in red top or serum separator tube for post sample (labeled POST).
Test Description
Cortisol Assay, 2 Samples: PRE (Baseline) and POST Dexamethasone Suppression.
This test measures cortisol concentrations before and after administration of exogenous dexamethasone (0-hours followed by an 8-hour sample). This is only a two cortisol assay. The low dose dexamethasone suppression test, a three cortisol sample test (CDEX3), is preferred for diagnosing hyperadrenocorticism. The high-dose dexamethasone suppression test, a three cortisol sample test, is used to differentiate pituitary-dependent from adrenal tumor hyperadrenocorticism.
Interferences: Marked hemolysis may affect results, and marked lipemia (if unable to be cleared by centrifugation) may falsely decrease cortisol levels.
Collection Method Instructions:
Cortisol levels are affected by previous/current steroid use (be it oral, topical, transdermal or inhaled). The exact period of withdrawal that is necessary to be able to accurately interpret cortisol levels is unknown however steroid type, dose, duration of use and method of administration all need to be considered.
For CDEX2 (the only sample that is acceptable is 0-hours and 8-hours).