Collecting blood for cryoglobulin analysis- All the processes and materials before serum collection must be kept warm at 37°C to avoid loss of cryoglobulin through clot formation and centrifugation.• Determination of cold agglutinins1. Isolated serum is placed in a refrigerator at 4°C for incubation for 7 to 14 days. Then, If there is a white precipitate to see, the test tube is subsequently placed in a 37°C water bath. The resultant precipitate redissolves in the serum; it is the real cryoglobulin.