Euglobulin Lysis Time (ELT)

Plasma, frozen

2 mL

1 mL

Blue-top (sodium citrate) tube

Do not draw from an arm with a heparin lock or heparinized catheter.

The euglobulin lysis time is a global nonspecific screen of the fibrinolytic system.

This is a semiquantitative assay. The diagnostic potential of euglobulin lysis times is limited by the extreme variation in lysis times among healthy individuals.⁶ Both hypofibrinogenemia and factor XIII deficiency may result in a shortened lysis time. In the case of hypofibrinogenemia, the shortened time is due to the decreased amount of fibrin to be lysed. In factor XIII deficiency, the clot is not stabilized by covalent cross-linking of fibers and can be readily lysed by plasmin. Traumatic venipuncture, prolonged stasis, or incorrect sample preparation may invalidate test results.

This test was developed and its performance characteristics determined by Labcorp. It has not been cleared or approved by the Food and Drug Administration.

The euglobulin fraction of the plasma refers to plasma proteins that precipitate at low pH and decreased ionic strength.⁶ In the ELT test, plasma inhibitors of fibrinolysis are physically removed and the reaction of fibrinogen, plasminogen, and plasminogen activators are assayed. The precipitate also includes tissue plasminogen activators, plasminogen, plasmin, and fibrinogen. The inhibitors of lysis, α₂-antiplasmin, and α₂-macroglobulin, do not precipitate. In the test system, the euglobulin precipitate is redissolved in buffer, and clotting is initiated with calcium. The assay is performed in a microtiter plate. The time required for the intrinsic plasmin to lyse the fibrin clot equates to the euglobulin lysis time.

The euglobulin lysis time (ELT) test provides an overview of the fibrinolytic system function by measuring the time it takes for an in vitro clot to dissolve in the absence of plasmin inhibitors.⁶ The fibrinolytic system is initiated following activation of the contact factors in the coagulation cascade. Fibrinolytic system activation leads to the production of plasmin, a proteolytic enzyme capable of degrading fibrin and fibrinogen as well as other plasma proteins. Increased fibrinolytic activity is suggested by clot lysis that occurs in less than two hours. A shortened ELT result implies excessive fibrinolytic activity that may be primary or could be secondary to inflammation, malignancy, trauma, fracture, liver disease, or thrombolytic therapy. Clinical bleeding is a possible consequence of excessive fibrinolysis. Excessive fibrinolysis may result from increased levels of tissue plasminogen activator (TPA), increased plasmin activity, decreased levels of plasminogen activator inhibitor-1 (PAI-1), or decreased α₂-antiplasmin activity. The effect of fibrinolysis is the production of plasma fibrin(ogen) degradation products (FDP or FSP) and D-dimer fragments. A prolonged ELT result implies a defect in the fibrinolytic system such as elevated plasminogen activator inhibitor (PAI-1) levels, elevated levels of α₂-antiplasmin, a plasminogen deficiency, or decreased tissue plasminogen activator (TPA) activity. The ELT may also be prolonged if the fibrinogen level exceeds 600 mg/dL. Inadequate fibrinolysis may be associated with superficial or deep vein thrombosis, pulmonary embolism, coronary thrombosis, transient ischemic attack, or stroke.