- Plasma is the supernatant obtained after centrifugation of blood collected into a test tube containing anticoagulant to prevent clotting
- Several anticoagulants are used in laboratory practice, the most common being lithium heparin and ethylenediaminetetraacetic acid (EDTA).
- Heparin prevents clotting by binding to thrombin.
- EDTA and citrate bind Ca2+ and Mg2+, thus interfering with the action of calcium and magnesium-dependent enzymes involved in the clotting cascade.
- Citrate is used as an anticoagulant when blood is collected for transfusion.
- Serum, on the other hand, is the supernatant obtained after a blood sample has been allowed to clot spontaneously (this usually requires 30–45 minutes). During clotting, fibrinogen is converted to fibrin as a result of proteolytic cleavage by thrombin, and so a major difference between plasma and serum is the absence of fibrinogen in serum.
Plasma and Serum Comparision
