D Dimer

Excerpt

The D-dimer is a by-product of the blood clotting and break-down process that can be measured via analysis of a blood sample. D-dimer is released when a blood clot begins to break down.

More specifically, platelets in the blood are connected to a D subunit. When blood clots form, the D group between two platelets form a bond. Many platelets bound together via D-Dimers (along with other factors, such as fibrin) form a clot. As part of the healing process of the body, clots that are formed begin to break down almost as soon as they are formed. When the clot bonds break, the D-dimer (D==D) breaks apart from the platelet (P):

D--P--D + D--P--D → D--P--D==D--P--D → D--P + D==D + P--D

Sensitivity and specificity vary based on the type of assay ordered. However, D-dimers have a high sensitivity but low specificity for detecting pulmonary embolism or deep vein thrombosis in low-risk populations.