Collect SST/2.5 mL serum, allow to clot for 30 minutes, centrifuge, transfer serum to a screw top plastic vial, indicate sample type on tube and send frozen on dry ice.

Alternate collection:
Collect red top, lavender EDTA or green top heparin, centrifuge within 1 hour of collection, transfer 2.5 mL serum/plasma to a screw top plastic vial, indicate sample type on tube and send frozen on dry ice.

Critical frozen.