D-dimer physiology

D-dimer is fibrin degradation product (FDP) resulting from the sequential break down of fibrin by the enzymes thrombin, factor VIII and plasmin.

Fibrin degradation products (FDPs) are formed whenever fibrin is broken down by enzymes. In fact, FDP are formed as a result of the sequential actions of the following three different enzymes: thrombin, factor VIII and plasmin. Determining FDPs is not considered useful, as this does not indicate whether the fibrin is part of a blood clot (or being generated as part of inflammation).

D-dimers are unique in that they are the breakdown products of a fibrin mesh that has been stabilized by Factor XIII. This factor crosslinks the E-element to two D-elements. This is the final step in the generation of a thrombus.

Plasmin is a fibrinolytic enzyme that organizes clots and breaks down the fibrin mesh. It cannot, however, break down the bonds between one E and two D units. The protein fragment thus left over is a D-dimer.^[1]

Shown below is an image summarizing the formation of D-dimers and other fibrin degradation products as a result of the sequential action of the three enzymes: thrombin, factor VIII and plasmin.

Three genetic variants, F3, F5, and FGA, were associated with D-dimer levels accoding to data based on 13 cohorts involving 21 052 healthy individuals from 13 European ancestry. The locations of the three genetic variants F3, F5, and FGA are 1p22 1q24 and 4q32 respectively.^[2]

Template:WH Template:WS