Human serum solidifying at 4C? - (Nov/13/2007 )
We are collecting human blood into "red top" tubes (no additives) and then centrifuging at 4C to seperate serum for collection however some of our tubes seperate fine but then the serum is very thick like jello so we cannot aliquot it. Anyone have any ideas why? Any suggestions to stop this?
Thank you in advance for your help!
Do you spin the blood immediately after collection? If so, I suspect that what you describe is a fibrin clot and you're collecting the PLASMA fraction of the blood, NOT serum; these are not the same and are not interchangable, since plasma contains platelets, fibrin/fibrinogen and a lot of thrombin, which is a very efficient protease!!!. Perhaps you could let the tubes rest for a while to allow the clot to form on its own - it will be ready in about ~30 minutes in normal individuals. After the clot forms, (it's readily visible) you can then centrifuge to collect the and the SERUM which will be separate from the cellular/platelet/fibrin fraction. Cheers
JAH is correct. The clotting agent in the red tops needs 30 minutes to clot the proteins. There are other agents for faster results. Like adding CaCl and thrombin.