Thromboelastography (TEG)

The TEG is not often found in a clinical coagulation laboratory. Instead, it is most often used as a point-of-care instrument for screening the clotting system during open heart surgery or liver transplantation. However, it can provide a global assessment of clot formation, providing information on platelet function, coagulation and fibrinolysis.

In principle, a whole blood sample is placed into a disposable plastic cup, into which is immersed a disposable plastic pin. The instrument rotates the cup and while the blood is fliud, no motion is transmitted to the pin. Any rotational movement is monitored by a computer via a fine torsion wire. As soon as clot begins to form, however, the movement of the cup is trasmitted to the pin in direct proportion to the strength of the forming clot. The TEG actually measures the shear elasticity of the clot. The graphic output is monitored in real time. Since clot breakdown is reflected by a reduction in amplitude, the TEG also represents a rapid and convenient means of diagnosing hyperfibrinolysis.

The TEG produces a graphical output with several parameters that describe different aspects of the clotting process. These include R (analogous to clot time), angle (rate of clotting), and maximal amplitude (maximum clot strength). Return of the tracing to towards the baseline indicates ongoing fibrinolysis.