Plasma, unlike whole blood, does not naturally clot. Whole blood clots because it contains platelets and clotting factors which initiate a complex cascade of reactions leading to fibrin formation, a protein mesh that traps blood cells to form a clot. Plasma, however, is the liquid component of blood after the cellular components (including platelets) have been removed. Therefore, to obtain serum (plasma without clotting factors), you must first allow whole blood to clot.
Obtaining Serum from Whole Blood: A Step-by-Step Guide
The process involves these steps:
- Collection: Collect a sample of whole blood.
- Clot Formation: Allow the whole blood to clot naturally by leaving it undisturbed at room temperature. This typically takes 15-30 minutes. The reference provided states: "After collection of the whole blood, allow the blood to clot by leaving it undisturbed at room temperature. This usually takes 15–30 minutes."
- Centrifugation: After clotting, centrifuge the sample at a speed of 1,000–2,000 x g for 10 minutes in a refrigerated centrifuge. This separates the clot from the serum (plasma without the clotting factors). The reference explains this by stating: "Remove the clot by centrifuging at 1,000–2,000 x g for 10 minutes in a refrigerated centrifuge. The resulting supernatant is designated serum."
- Serum Collection: The resulting supernatant liquid is serum.
Therefore, you don't clot plasma directly; instead, you obtain serum from the clotting of whole blood.
