What is the Difference Between D Dimer and FDP?

D-dimer and fibrin degradation products (FDPs) are both fragments released during the process of fibrinolysis, which is the degradation of the fibrin network that takes place after the clotting process. However, there are some differences between the two:

• Structure: D-dimer is a specific fragment formed only upon the degradation of cross-linked fibrin, containing extra linkages of D and E subunits of fibrin. In contrast, FDPs do not contain these extra linkages.
• Sensitivity and Specificity: D-dimer is more specific for actual clots than FDPs, as it is only produced from the breakdown of real clots (not from the breakdown of fibrinogen). FDPs can become elevated whenever the coagulation and fibrinolytic systems are activated.
• Clinical Use: D-dimer tests are often used to rule out a thrombus, but they are not very specific for diagnosing a thrombus. FDP tests are used to analyze the risk of atherosclerosis and can be performed as coagulation tests.
• Detection: Tests that specifically look for D-dimers were developed in the 1990s, and most labs use these D-dimer assays now instead of assays that measure FDPs.

In summary, D-dimer and FDP are both degradation products of fibrinolysis, but they differ in structure, sensitivity, specificity, and clinical use. D-dimer is more specific for actual clots, while FDPs can be elevated during the activation of the coagulation and fibrinolytic systems.

Comparative Table: D Dimer vs FDP

D-dimer and fibrin degradation products (FDPs) are both indicators of blood clot formation and degradation, but they have some differences in structure and specificity. Here is a table highlighting the differences between D-dimer and FDPs:

In summary, D-dimer is a more specific marker for blood clot formation and degradation compared to FDPs. D-dimer tests are more commonly used in diagnostic settings, while FDP tests have been largely replaced due to their lower specificity.