Plasma and serum are two components of blood, and they have some key differences. Here are five distinctions between plasma and serum:
Composition:
Plasma: Plasma is the liquid component of blood that remains after blood has clotted. It makes up about 55% of total blood volume. Plasma contains water, electrolytes, proteins (including clotting factors), hormones, and waste products.
Serum: Serum is similar to plasma but does not contain clotting factors. It is the liquid portion of blood obtained after coagulation has taken place, meaning that blood has clotted and the clot has been removed. Therefore, serum lacks the proteins involved in blood clotting.
Clotting Ability:
Plasma: Plasma retains its clotting ability because it includes all the proteins necessary for blood clotting (coagulation factors). It is anticoagulated when collected for certain laboratory tests.
Serum: Serum does not clot because it is obtained after the blood has coagulated and the clot has been removed. It is typically used for tests where clotting factors are not needed.
Collection Process:
Plasma: Plasma is obtained by anticoagulating blood using an anticoagulant such as heparin or EDTA to prevent clotting. This is often done for tests that require the measurement of clotting factors or other blood components.
Serum: Serum is obtained by allowing blood to clot, and then the clot is separated from the liquid portion (serum). This is the preferred sample for tests where the presence of clotting factors is not required.
Storage and Stability:
Plasma: Plasma can be stored for a more extended period because it contains anticoagulants that prevent clotting. Plasma can be used for various laboratory tests over an extended period.
Serum: Serum is generally less stable than plasma and may have a shorter storage life. It is often recommended to separate serum from the blood cells and store it at lower temperatures to maintain stability.
Use in Laboratory Testing:
Plasma: Plasma is used for tests that require the measurement of clotting factors, such as coagulation studies, fibrinogen levels, and other tests related to blood clotting.
Serum: Serum is commonly used for tests that do not require the measurement of clotting factors, such as blood glucose, electrolyte levels, and certain enzyme assays.
In summary, while plasma and serum are both components of blood, the key difference lies in the presence of clotting factors. Plasma contains clotting factors, while serum is obtained after the blood has clotted and lacks these factors. The choice between plasma and serum for laboratory tests depends on the specific requirements of the tests being conducted.