Difference Between D Dimer and FDP

Key Difference – D Dimer vs FDP
 

Fibrinogen is one of the main components involved in blood clotting process. Fibrinogen is the protein in which the fibrin network is formed upon injury to tissue. This process is known as blood clotting. Fibrinolysis is the process where the fibrin is broken down by the action of plasmin. These degradation products are known as Fibrin Degradation Products (FDPs). Fibrin Degradation Product or FDP is a product of fibrinolysis that remains after the clot has been dissolved. D Dimer is the final product of fibrin degradation and is a type of FDP. The key difference between FDP and D Dimer is the structure. FDP do not contain extra linkages of D and E subunits of Fibrin, whereas D dimer is composed of extra linkages.

CONTENTS

1. Overview and Key Difference
2. What is D Dimer
3. What is FDP
4. Similarities Between D Dimer and FDP
5. Side by Side Comparison – D Dimer vs FDP in Tabular Form
6. Summary

What is D Dimer?

D Dimer is the final end product of fibrinolysis. It is the type of a Fibrin Degradation Product. It has a molecular weight of 180 kDa and is composed of extra linkages with D and E subunits of fibrin. Thus, D dimer is composed of remnants of all three chains of fibrinogen that are termed as; alpha, beta and gamma. These chains are cross-linked with disulfide bonds. D Dimer attains a dimeric structure as the name suggests. The dimeric structure of D dimer is held by isopeptide bonds between the gamma chains. They are intermolecular covalent bonds.

The D dimer test is a test done to the analysis of cardiac health and atherosclerosis. D dimer levels of healthy individuals lie below 0.5 µg/ml whereas, elevated levels suggest thrombosis, pulmonary embolism and atherosclerosis. Monoclonal antibodies are used in the D dimer test to precisely identify the levels of antibodies. This test is much error prone due to the existence of many FDPs similar to D dimer.

What is FDP?

Fibrin Degradation Product or FDP is the remnant of fibrinolysis, and is the process in which a blood clot is dissolved or disintegrated. FDPs remain in the bloodstream upon fibrinolysis. Upon tissue injury, the blood clotting factors, platelets and other cofactors combine together to form a fine network of fibrin that will act as a net over the injury until it is healed. Once the tissue healing process is completed, the blood clot is broken down and dissolved by an enzymatic process that utilizes Plasmin. The cross-linked fibrin network is disintegrated to produce FDPs.

FDP testing is done to analyze for cardiac health and atherosclerosis. Similar to D dimer test, elevated levels of FDP will suggest thrombosis, atherosclerosis and pulmonary embolism.

What are the Similarities Between D Dimer and FDP?

• Both D Dimer and EDP are degradation products of fibrinolysis
• Both D Dimer and EDP molecules are analyzed for thrombosis, atherosclerosis and pulmonary embolism.
• Both tests involving FDP and D dimer are done as coagulation tests.
• Plasmin is involved in the degradation of fibrin, to yield both FDP and D dimer.

What is the Difference Between D Dimer and FDP?

Summary – D Dimer vs FDP 

D dimer and FDP are degradation products of fibrinolysis, whereas the most terminal dimeric end product is the D dimer. Fibrinolysis, or degradation of the fibrin network takes place as a post event for the clotting process. Plasmin is involved in the degradation process that will yield both FDP and D dimers. Both these components are used as laboratory test specimens to analyze the risk of atherosclerosis. This is the difference between D Dimer and FDP.

Reference:

1.“Fibrin Degradation Products (FDP): What Is it?” Healthline, Healthline Media. Available here 
2.“What Is the D-Dimer Test?” WebMD, WebMD. Available here 

Image Courtesy:

1.’D-Dimère’By Pocout – Own work, (CC BY-SA 3.0) via Commons Wikimedia 
2.’Fibrinolysis’By Jfdwolff at en.wikipedia, (CC BY-SA 3.0) via Commons Wikimedia