Difference Between Serum and Plasma

Main Difference – Serum vs Plasma

Serum and plasma are two derivatives of blood which lack blood cells like red blood cells, white blood cells, and platelets. Both contain proteins, drugs, hormones, toxins, and electrolytes. Both serum and plasma have therapeutic and diagnostic uses. They can be separated from blood by centrifugation, which removes the cellular portion of blood. Anticoagulants are added to blood once it is transfused in order to prevent clotting. The serum is amber-colored but plasma is straw-colored. The main difference between serum and plasma is that serum is the protein-rich liquid, which separates out when blood coagulates whereas plasma is the liquid component of blood which holds blood cells in whole blood in suspension. 

This article looks at,

1. What is Serum
      – Definition, Composition, Properties
2. What is Plasma
      – Definition, Composition, Properties
3. What is the difference between Serum and Plasma

What is Serum

The serum is an amber-colored, watery portion of animal blood, which remains after blood coagulation. Hence, serum lacks blood cells like red blood cells, white blood cells, and platelets. It also lacks clotting factors like fibrinogen. But, serum contains all the proteins like albumin, and globulin that are not involved in blood coagulation process. It also contains antibodies, antigens, electrolytes, hormones, drugs, and microorganisms. Serology is the study of serum. The serum is separated from blood by centrifugation, which removes the cellular component of blood, which is followed by coagulation. Coagulation removes clotting factors like fibrinogen, prothrombin, and tissue thromboplastin from the blood. The serum is a good source of electrolytes. It is used for various diagnostic tests for hormones and enzymes. It is used for the determination of blood groups as well. Animal sera are used as anti-venom, anti-toxins, and vaccinations. The serum can be stored at 2-6 ºC for several days.

Figure 1: Serum, separated from blood

What is Plasma

Plasma is the liquid portion of blood. It is a straw-colored, protein-salt solution which suspends blood cells and platelets. Hence, plasma serves as an extracellular fluid. It takes up 55% of the total volume of blood. The water content in the plasma is about 92%. Plasma contains dissolved proteins like albumin, globulin, and fibrinogen, glucose, clotting factors, hormones, electrolytes, carbon dioxide, and oxygen. It maintains a satisfactory blood pressure and volume, balances the body pH, and serves as a medium for exchanging minerals like sodium and potassium.

Plasma is separated from its cellular portion by centrifugation. Four units of plasma are diluted with one part of the anticoagulant, citrate phosphate dextrose (CPD) up to a total volume of 300 mL. When the plasma sample is frozen within 8 hours of collection, it is called fresh-frozen plasma (FFP). When it is frozen longer than 8 hours but less than 24 hours, the plasma sample is called frozen plasma (FP). After preservation by adding anticoagulants, frozen plasma can be stored up to one year at -18 ºC. Plasma transfusion is done for trauma patients, patients with severe liver diseases, and in multiple clotting factor deficiencies. Plasma derivatives like special plasma proteins can be obtained by fractionation.  Viruses that cause HIV, hepatitis B and C are destroyed by treating with heat or solvent detergents. Scheme of a blood sample after centrifugation is shown in figure 2.

Figure 2:  Scheme of a blood sample after centrifugation

Difference Between Serum and Plasma

Definition

Serum: Serum is an amber-colored, protein-rich liquid, which separates when blood coagulates.

Plasma: Plasma is a straw-colored, liquid component of blood in which blood cells are suspended.

Correspondence

Serum: Serum is the part of the blood which does not contain blood cells and clotting factors.

Plasma: Plasma contains serum and clotting factors.

Acquired From

Serum: Serum is acquired from the spinning after clotting.

Plasma: Plasma is acquired from the spinning before clotting.

Separation

Serum: No anticoagulants are required for the separation of serum from blood.

Plasma: Anticoagulants are required for the separation of plasma from blood.

Separation Process

Serum: Serum is difficult to separate and time-consuming.

Plasma: The separation of plasma is comparatively easier and less time-consuming compared to serum.

Volume

Serum: The volume of serum is less than that of plasma.

Plasma: Plasma takes 55% of total volume of blood.

Clotting Factors

Serum: Serum lacks clotting factors.

Plasma: Plasma consists of clotting factors.

Density

Serum: The density of serum is 1.024 g/ml.

Plasma: The density of plasma is 1.025 g/ml.

Water

Serum: Serum contains 90% of water.

Plasma: Plasma contains 92-95% of water.

Medical Use

Serum: Serum is used for enzyme tests and hormone tests.

Plasma: Plasma transfusion is done for trauma patients, patients with severe liver diseases, etc.

Storage

Serum: Serum can be stored at 2-6 ºC for several days.

Plasma: After preservation by adding anticoagulants, frozen plasma can be stored up to one year at -18 ºC.

Conclusion

Serum and plasma are two derivatives of blood. Plasma is the liquid portion of the blood in which the blood cells are suspended. It is a protein-rich liquid. The serum is the liquid portion which is left after blood coagulation. Hence, serum lacks proteins which are involved in the coagulation like fibrinogen. Both serum and plasma have medical uses. However, the main difference between serum and plasma is in the differential isolation processes of both of derivatives.  

 Reference:
1.”Blood Serum.” Merriam-Webster. Merriam-Webster, n.d. Web. 27 May 2017. <https://www.merriam-webster.com/dictionary/blood%20serum>.
2.”Medical Definition of Serum.” MedicineNet. N.p., n.d. Web. 27 May 2017. <http://www.medicinenet.com/script/main/art.asp?articlekey=5470>.
3.”Plasma.” American Red Cross. N.p., n.d. Web. 27 May 2017. <http://www.redcrossblood.org/learn-about-blood/blood-components/plasma>.
4. Hess, John R. “Conventional blood banking and blood component storage regulation: opportunities for improvement.” Blood Transfusion. Edizioni SIMTI — SIMTI Servizi Srl, June 2010. Web. 27 May 2017. <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2897192/>.

Image Courtesy:
1. “Blood-centrifugation-scheme” By KnuteKnudsen at English Wikipedia (CC BY 3.0) via Commons Wikimedia