Difference between Plasma and Serum

Updated on July 25, 2018

In the medical field, the terms “plasma” and “serum” are commonly used interchangeably. Although they are closely linked, they are completely different blood components that have distinct functions in the body.

Summary Table

PlasmaSerum
Contains fibrinogenDoes not contain fibrinogen
Isolated from other blood components by the use of centrifugationIsolated from other blood components by the use of plasmapheresis
Involves the use of anticoagulants during isolationDoes not involve any anticoagulants during isolation
Transports nutrients to the body’s organs and delivers waste products from metabolic cells to excretory organsRenews embryonic stem cells and acts as a potent antibody against life-threatening pathogens when used pharmaceutically
Transfused to patients that are low in blood cellsMainly used in diagnosing diseases by the use of blood testing methods

Definitions

test tubes
Plasma suspended at the top of test tubes

Plasma is a watery solution that makes up approximately 55% of the total blood volume. It is also found in the lymphatic fluid, and it is rich in protein and electrolytes.

Serum suspended
Serum suspended at the top of the test tube

Serum is a clear, amber-colored liquid extract derived from blood coagulation. It is made up of protein, antibodies, electrolytes, and other blood components.

Plasma vs Serum

Despite their strong associations, there is a major difference between plasma and serum.

Components

Plasma and serum have major similarities in terms of composition, except that serum does not contain fibrinogen – a soluble plasma protein that converts into fibrin when the blood clots. Functioning mainly as a solvent for nutrients, electrolytes, proteins, and other components, plasma is made up of around 91.5% water. Both plasma and serum contain protein, antibodies, electrolytes, hormones, gases, antigens, and other substances necessary to sustain life.

Isolation Stages

Between the two, the isolation of serum involves a more complex process. Plasma is extracted by the use of a centrifuge – a scientific device used to isolate solids from liquid blood components. As the blood quickly spins inside the device during centrifugation, the heaviest particles are forced to sink into the bottom part of the vial. After spinning, the red blood cells, which are the heaviest blood component, sit at the bottom, and atop it are layers of white blood cells, platelets, and plasma, which is the lightest part of the blood.

Serum isolation, on the other hand, involves plasmapheresis – a procedure where blood plasma is extracted, treated, and reintegrated. Once plasma is isolated by centrifugation, the anti-coagulated blood is left at room temperature for about 10-15 minutes to allow blood coagulation. The coagulated blood sinks into the bottom of the tube, while serum is suspended at the top.

Use of Anticoagulants

During plasma isolation, an anticoagulant is added to the blood sample to prevent blood clotting. Serum isolation, by contrast, does not involve any anticoagulants.

Bodily Function

Both these blood components are essential in maintaining holistic wellness. Plasma plays a critical role in transporting nutrients to the body’s organs and delivering waste products from metabolic cells to the liver, kidneys, and other excretory organs. Meanwhile, serum, together with the cytokine leukemia factor, is integral in the renewal of embryonic stem cells. In the biopharmaceutical field, serum is also used as a potent antibody against life-threatening pathogens. The serum extracted from patients who have recovered from an infection is rich in antibodies that can be used in immunotherapy.

Medical Use

In the medical field, plasma is transfused to patients that are low in blood cells, while serum is mainly used in diagnosing diseases through blood testing methods.

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