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A Practical Guide to Laboratory Haemostasis

 

Euglobulin Clot Lysis Time [ECLT]



Introduction

The euglobulin clot lysis time is a test that reflects the overall fibrinolytic activity of plasma. In many cases (perhaps all) it has now been replaced by specific functional and immunological assays. The TEG often serves to monitor fibrinolysis and is a considerably more rapid test to perform than the ECLT.


TAFI Thrombin-Activatable Fibrinolysis Inhibitor
XL-Fibrin Cross-Linked Fibrin
α2-AP Alpha 2 antiplasmin
t-PA
Tissue Plasminogen Activator
u-PA Urinary Plasminogen Activator
scu-PA Single Chain Urinary Plasminogen Activator

Principles & Method

Venous blood is collected into chilled tubes containing trisodium citrate as an anticoagulant and placed on ice. The sample is then centrifuged at 4°C, the plasma sample is collected, diluted with acetic acid and incubated on ice for 15 minutes. A precipitate forms [the euglobulin fraction of plasma] which contains plasminogen, plasminogen activators [primarily t-PA] and fibrinogen. The supernatant is collected by centrifugation at in refrigerated centrifuge at 4°C. The supernatant is discarded and the precipitate is dissolved in buffer. This is then clotted with thrombin and the time to clot lysis determined by inspection every 15 minutes.

A control plasma sample collected at the same time as the patient sample must be run in parallel.

Fibrin Plate Lysis

A fibrinogen solution is poured onto a Petri dish and clotted with thrombin and Calcium Chloride to form fibrin 'lawns.' The euglobulin fraction under test is carefully pipetted onto the fibrin lawn. The plates are incubated at 37°C . The plasminogen in the lawn is converted into plasmin which leads to lysis of the fibrin lawn. The diameter of the zones of lysis are proportional to the concentration plasminogen activator in the euglobulin fraction. By running controls in parallel, zones of lysis which are larger than the control demonstrate hyperfibrinolysis whilst zones which are smaller show hypofibrinolysis.

Interpretation

Abnormalities of fibrinolysis are common and can be both physiological and pathological:

  Increased Fibrinolysis [Decreased ECLT] Decreased Fibrinolysis [Increased ECLT]
Physiological Normal diurnal variation
Exercise
Venous Occlusion
Normal diurnal variation
3rd trimester of Pregnancy
Pathological Factor XIII Deficiency
In association with thrombolytic therapy e.g. t-PA, streptokinase
Following treatment with DDAVP
DIC
Liver disease
During the anhepatic phase of liver transplantation
Post-operatively
In association with obesity
In many cases of recurrent venous thromboses the significance of which is unclear


Reference Ranges

Reference Range: 90-240 minutes
Hyperfibrinolysis: <60 minutes
Hypofibrinolysis: >240 minutes

What Test Next

In individuals with an abnormal ECLT, it may be useful to undertake specific assays of the components of the fibrinolytic pathway or to perform a TEG.

Data Interpretation

Click HERE to go to the Data Interpretation Exercises.