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.
Room temp: 72 hours, Refrigerated: Unacceptable, Frozen: Unacceptable
Cryoglobulins are a group of proteins which precipitate from serum, plasma or urine upon exposure to cold.