Immediately following collection, mix sample by gently inverting 5 times
Amber transfer vial/tube - 12 mL (LabCorp)
If amber tubes are unavailable, cover standard transport tube completely, top and bottom, with aluminum foil and secure with tape
Ambient (preferred) - 14 days
Refrigerated - 14 days
Frozen - 14 days
Freeze/thaw cycles - stable x3
High-pressure liquid chromatography (HPLC)
3 - 91 µg/dL