• Serum - Blood outside of the human body is designed to clot. This natural function prevents bleeding. If blood is drawn into a tube without anticoagulant: plain red or SST, then the blood will clot naturally and separate into liquid and cells. This liquid is called serum. It is the fluid portion of a blood clot. It does not contain fibrinogen, therefore coagulation tests cannot be performed because the coagulation factors (fibrinogen) have been used in the process of clot formation.
    
• Plasma - If anticoagulants are added to the tube: EDTA, Sodium citrate, heparin, etc., the blood will not clot. Blood outside the body with anticoagulant is referred to as whole blood. Whole blood can still be separated into liquid and cells. This liquid is called plasma. It is the liquid portion of blood when the tube contains anticoagulant. The use of an anticoagulant preserves the fibrinogens in the plasma, so it may be used in a coagulation test. 

 

Difference between Serum and Plasma

Plasma and serum are derived from the liquid portion of the blood, yet the difference between plasma and serum is quite apparent. Read on to find out how they differ.

Blood is a fluid connective tissue which travels throughout the body by transporting necessary nutrients, oxygen, and metabolic wastes. It is also involved in the regulation of the body’s temperature and the pH levels by interacting with acids and bases.

Blood is primarily composed of RBC (red blood cells), WBC (white blood cells), plasma, and serum. Plasma and serum are the main components of blood and are routinely used in blood group test experiments for determining the patient’s blood group.

Plasma and serum can be separated by centrifugation of blood on the basis of weight, size, and density. The serum is the liquid obtained after blood is allowed to clot, whereas plasma is obtained after treating blood with anticoagulation compounds.

Also Read: Difference between blood and lymph

Read on to explore the difference between plasma and serum.

Difference between Plasma and Serum

Serum and plasma are obtained from the liquid portion of the blood that is obtained when the cells are removed. However, there is striking difference between plasma and serum. Serum is the liquid that remains after the clotting of blood. Whereas, plasma is the liquid that remains when anticoagulant is added to prevent clotting.

Following are the important difference between plasma and serum:

Plasma	Serum
A transparent, straw-coloured, liquid portion of the blood.	An undiluted fluid, the extracellular portion of blood.
It is composed of serum and clotting factor.	It is the part of the blood which lacks clotting factor.
It is acquired after centrifuging blood with the anticoagulant.	It is acquired after centrifuging of coagulated blood.
Anticoagulant is required to obtain plasma from the blood sample.	Anticoagulant is not required to separate the serum from the blood sample.
Consists of 55% of the total volume of blood.	Less volume in comparison to plasma.
Comparatively easier and less time is required to separate the plasma from the blood sample.	Difficult to separate serum from the blood sample. It is a time-consuming process.
Contains fibrinogen.	Lacks fibrinogen.
Consists of 92% water with proteins, salts, lipids, and glucose.	Consists of 90% water with dissolved hormones, proteins, minerals, and carbon dioxide.
Has 1.025 g/ml density	Has 1.024 g/ml density.
Has a long shelf life. It can be preserved up to ten years.	Has a short shelf life. It can be preserved only for a few months.
Plasma is the main medium for excretory product transportation.	An important source of electrolytes.
Cells are freely suspended in plasma.	Cells are attached together by clot formation.

What is Plasma?

Plasma is the medium of the blood, in which different types of blood cells exists. Red blood cells, white blood cells and other components of blood are suspended in plasma.

• Plasma is the liquid part of the blood. It contains the clotting agent fibrinogen, which prevents the excessive flow of blood during injury. It also contains proteins which help in the transportation of glucose and other nutrients to different parts of the body.
• Plasma helps in the regulation of body temperature.
• It is also responsible for controlling blood pressure.
• Plasma is obtained in the upper layer during centrifugation. It is separated to increase the longevity up to years and also to make it easier to carry it from one place to another.

What is Serum?

The serum is the liquid or undiluted part of the blood, which lacks clotting factors. Hence, it is formed after blood coagulation. The serum helps in the diagnosis of diseases such as blood pressure, sugar, cholesterol, etc.

For more information on the difference between plasma and serum, keep visiting BYJU’S website or download BYJU’S app.

Also Read: Body fluids and circulation

Frequently Asked Questions

1. What are the advantages of plasma over the serum?

Plasma contains the most commonly used anticoagulant heparin. It acts through a complex it forms with anti-thrombin-III. Anti-thrombin III is a protein that prevents blood clotting.

2. What is serum?

Serum is the plasma from which the clotting factors have been removed.

3. What is the difference between blood and plasma?

Plasma is the translucent part of blood other than RBCs, WBCs, platelets and other cellular components. It helps to clot blood and is composed of 90% water.

4. How is the plasma collected from the body?

Collection of plasma requires a lot of time. It takes around an hour to collect plasma from the body. The blood is drawn from the body with the help of a needle placed in the arm, and the plasma is separated from the red blood cells, white blood cells and platelets.

5. Why is the serum test conducted?

The serum is done to measure the amount of protein albumin in the blood. When the kidney starts to fail, the albumin starts leaking in the urine. The serum test helps to diagnose liver and kidney abnormalities.

Serum and plasma tubes

The commercially available serum tubes are as follows:
Red	No anticoagulant.
Red with black	Treated with gel to help to separate the clot (not evaluated).

The commercially available plasma tubes are as follows:
Lavender	Treated with EDTA.
Blue	Treated with citrate.
Green	Treated with heparin.
Grey	Treated with potassium oxalate/sodium fluoride (not evaluated).
Yellow	Treated with potassium oxalate/sodium fluoride (not evaluated).

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