Overnight fasting is preferred.

Collect red top, place in a 37°C water bath, oven, incubator or heat block to clot for 1 hour. Centrifuge in a warm centrifuge (can be warmed by running for 10 minutes prior) then transfer 3 mL serum to a screw top transport tube, indicate sample type on tube and send room temp.

If the sample is NOT kept at 37° C during all processing steps, the cryoprecipitate if present can precipitate out of solution and be lost in the clot or during the centrifugation process and result in a false negative result.