The euglobulin lysis time (ELT) is a test that measures overall fibrinolysis. The test is performed by mixing citrated platelet-poor plasma with acid in a glass test tube. This acidification causes the precipitation of certain clotting factors in a complex called the euglobulin fraction. The euglobulin fraction contains the important fibrinolytic factors fibrinogen, PAI-1, tissue plasminogen activator (tPA), plasminogen, and to a lesser extent alpha 2-antiplasmin. The euglobulin fraction also contains factor VIII.
After precipitation, the euglobulin fraction is resuspended in a borate solution. Clotting is then activated by the addition of calcium chloride at 37 C. Historically, subsequent amount of fibrinolysis was determined by eye, by observing the clot within the test tube at ten minute intervals until complete lysis had occurred. Newer automated methods have also been developed. These methods use the same principle as the older technique, but use a spectrophotometer to track clot lysis as a function of optical density.