One 6 mL gray (potassium oxalate/sodium fluoride) top tube. Also acceptable: plain red, lavender (EDTA), pink (K2EDTA) or green (sodium heparin) top tubes.

2 mL serum or plasma at 2-8°C (Min: 1 mL). Separate serum/plasma from cells within 2 hours of collection.

After separation from cells: Ambient: 1 week; Refrigerated: 2 weeks; Frozen: 3 years (Avoid repeated freeze/thaw cycles)

Gel separator tubes, whole blood or plasma collected in light blue (sodium citrate) tubes.