A Complete Study Of Serum VS Plasma: Definition, Differences & More

Serum VS Plasma: Plasma and serum are acquired from the liquid portion of the blood, yet the difference between plasma and serum is quite possible. Read on to find out how they diverge.

Blood is a fluid combinative tissue that travels throughout the body by transporting mandatory nutrients, oxygen, and metabolic devastations. It is also associated with the regulation of the body’s temperature and pH levels by meshing with acids and bases.

Blood is mainly composed of RBC (red blood cells), WBC (white blood cells), plasma, and serum. Plasma and serum are the main ingredients of blood and are consistently used in blood group test examinations for resolving the patient’s blood group.

Plasma and serum can be detached 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.

What is Plasma?

Plasma makes up about 55% of the total blood volume. It is the liquid fraction of blood and is 90% water. Other than water, plasma also consists of fibrinogen (which assists to the normal clotting of blood) and albumin (which creates to keep fluid in your bloodstream and prevent leaking into other tissues).

Serum VS Plasma
Serum VS Plasma

The function of plasma in the blood is to transport all the proteins, nutrients, antibodies, hormones, etc. all over the body. As the plasma races around the body, cells will invest their waste into the plasma, which contributes to another activity of the plasma: waste discharge.

What is Serum?

Put normally, the serum is plasma minus the clotting factors and blood cells. During the action of discharging the clotting factors (attained by centrifugation), the protein fibrinogen as described above is transformed to fibrin. Fibrin is an insoluble protein that is used to facilitate the repair of tissue damage by building a clot over the wound which acts to block the flow of blood.

What is the difference between Plasma and Serum?

A key difference between plasma and serum is that plasma is liquid, and serum is fluid. While most of the factors are the same for both plasma and serum, plasma consists of fibrinogen which is absent in serum.

Both plasma and serum can be derived from blood with the use of a centrifuge but it’s worth noting that serum is obtained after the clotting of blood, while plasma can be obtained before the coagulation of the blood. The serum is essentially used for blood typing but is also used for diagnostic testing. Plasma, on the other hand, is mainly used for blood-clotting-related problems.

Here we are comparing Serum and Plasma on the basis of various factors: 

  1. Definition: Serum is the clear yellow fluid separated when blood is allowed to clot freely while plasma is  Yellowish and slight alkaline fluid, in which blood cells float.
  2. Clotting factors: Serum is the watery fluid from blood without the clotting factors while plasma is the blood fluid that contains blood-clotting agents.
  3. Composition The serum contains proteins, electrolytes, antibodies, antigens, and hormones. Plasma contains all suspended blood cells with proteins, salts, lipids, glucose.
  4. Water content: The serum contains 90% water. Plasma contains 92-95% of water.
  5. Components: The serum contains proteins like albumin and globulins. Plasma contains clotting factors and water.
  6. Fibrinogen: In Serum Fibrinogen absent while in Plasma Fibrinogen present.
  7. Cell arrangement: Cells are usually attached together by clot formation Serum. Cells are not attached together and suspended in plasma.
  8. Method of Separation: Serum is acquired from the process of spinning after clotting while plasma is acquired from the process of spinning before clotting.
  9. Use of Anti-coagulant: Anticoagulant is not needed to separate the serum. An anticoagulant is required to obtain plasma.
  10. Feasibility of Separation: Separation of serum requires higher levels of expertise, expenses and is time-consuming. Separation of plasma is relatively easy and inexpensive
  11. Volume in blood: Serum has less volume in comparison to plasma while plasma consists of 55% of the total volume of blood.
  12. Density: The density of serum is 1.024g/ml. The density of plasma is 1.025g/ml.
  13. Storage: The serum can be stored at 2-6 degrees centigrade for several days. Frozen plasma can be stored for up to a year.
  14. Discoloration: The serum does not discolor on standing. Plasma tends to discolor on standing.
  15. Importance: The serum is the primary source of electrolytes while the function of the plasma is the transport of excretory metabolites and materials in the blood. It also helps in the maintenance of blood pressure and in the regulation of body temperature.
  16. Associated terms: The branch of study that deals with studying serum and analyzing it for diagnostic purposes are called serology. Plasmapheresis refers to the process of isolation of plasma from the blood using centrifugation.
  17. Uses: Human serum is usually used for the purpose of diagnostic testing. Other animal seras are used as anti-venom, antitoxins, and vaccinations. They are also used in humans for therapeutic purposes. Plasma is delivered to patients who lack blood cells. It is also Transferred to patients who suffer from hemophilia, shocks, burns, and other clotting problems.

The Coagulation Process Makes Serum Different From Plasma

To learn the differences, you must be attentive to how the plasma and serum are split from whole blood. The following points explain what laboratories do to get these varieties.

1. Blood is drawn from the patient. Blood samples for lab testing may be achieved in several ways. The most common method is venipuncture, the departure of blood from a vein using a needle and a collecting tube, which consists of different additives.

Plasma Seperated After Centrifugation.
Plasma Seperated After Centrifugation.

A tourniquet is bandaged around the arm above the venipuncture site, which begins blood to accumulate in the vein. This expanded blood volume makes the vein stand out, forming venipuncture more successful.

To assure that there is no confusion on the part of the phlebotomist in classifying the proper tube, the stoppers and closures of collecting tubes are color-coded. For example, the stopper of the collecting tube incorporating the additive EDTA (an anticoagulant) is lavender. This tube is used when you want to mix the blood with the anticoagulant EDTA to get plasma.

Conversely, if you wish to achieve serum you need to have the blood clot so you don’t need to use the tube with an anticoagulant. Therefore, the collecting tube to get serum is plain, color-coded red. Similarly, there are differ color-codes for anticoagulant as well as other additives such as a preservative.

Serum Immediately After Centrifugation.
Serum Immediately After Centrifugation.

2. The collecting tubes are centrifuged.

The tube with anticoagulants can be spun right away to obtain plasma. Whereas, the tube for serum must be stored for 30-45 minutes undisturbed, and, preferably, in the dark before centrifugation.

Separation mechanism

Whole blood in a collecting tube with anticoagulants gets you plasma after centrifugation. This is because the coagulability of the blood is inhibited by the addition of anticoagulants.

The heavier portion of the whole blood, the red blood cells settle at the bottom of the test tube. Then, the next layer is the buffy coat consisting of white blood cells and platelets. Plasma is virtually the remaining cell-free supernatant.

Whole blood in a plain collecting tube will give you serum after centrifugation is done 30-40 minutes post-blood collection. A standing time of 40 minutes is given to allow the blood to clot. This clot then contracts to ooze out the serum. Initially, the clot is the whole blood then after some time, it starts to release the fluid portion of it which is plasma except fibrinogen. There is no fibrinogen in the serum because it is converted into fibrin during the formation of the clot.

Serum Separated From Blood By A Gel Layer.
Serum Separated From Blood By A Gel Layer.

Laboratories use gel separators to improve the yield of specimens. The gel in a separator tube is a liquid polymer along with an organic or inorganic filler added to achieve the appropriate density of the gel.

3. The specimen is detached for analysis.

The next phase after centrifugation is to deliver the samples (plasma or serum) directly to the analyzer. Ideally, the analyzer desires to do this job by piercing the closed stopper and collecting thereby.

Manually, the plasma or serum is recollected using a transfer pipette. It is done attentively without distorting the other layers into another classified tube.

Exosome purification from serum and plasma

Both serum and plasma can be cleaned by simply going through an Exo-spin™ column. Alternatively, the serum/plasma sample can be processed before column function using the precipitant buffer. Mixing the sample with this buffer, pursued by centrifugation, removes many of the components of plasma and sera and allows greater numbers of exosomes to be purified on a single Exo-spin™ column.

Misconceptions About Serum vs Plasma

  • The serum does not contain clotting factors. This is false since clotting factors IX, X, XI, and VII/VIIa are found in serum.
  • Plasma is liquid and serum is fluid. This statement can be true if you are talking about serum as it oozes from the clot. But, to say that the plasma is liquid

FAQs about Plasma VS Serum

What Are The Advantages Of Plasma Over 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.

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.

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.

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 Into The Urine. The Serum Test Helps To Diagnose Liver And Kidney Abnormalities.