R value – Measure of coagulation time from start to initial fibrin formation.
Prolonged when there is coagulation factor deficiency, anticoagulation, severe thrombocytopenia or hypofibrinogenemia
K value: Represents clot kinetics – measuring time taken for a certain level of clot strength is reached i.e. width of the clot reaches 20 mm.
Prolonged when there is coagulation factor deficiency, hypofibrinogenemia, thrombocytopenia or thrombocytopathy.
Alpha angle: is the angle between midline and a line tangential to the developing “body” of TEG trace. Represents clot kinetics of clot build up and cross-linking.
This is increased in hypercoagulable states and decreaed in thrombocytopenia or hypofibrinogenemia.
MA: Maximum amplitude is the maximum width of the “body” of TEG trace. Represents ultimate clot strength.
Reflects platelet number and function & interaction of platelet with fibrin.
Increased in hypercoagulable states.
Decreased in thrombocytopenia, thrombocytopathy and hypofibrinogenemia.
Lysis: LY30 and LY60 – Clot lysis at 30 min and 60 min after MA.
Expressed as % of amplitude of TEG trace at 30 and 60 min in comparison to MA.
Increased in states of fibrinolysis.
Platelet function testing:
Sonoclot - an alternative for TEG. Uses ultrasonic vibration to stimulate clot formation.
VerifyNow (Accumetrics, San Diego , CA
Clot Signature Analyzer (CSA, Xylum, Scarsdale , NY
Platelet function analyzer, PFA-100 (Dade Behring, Miami , FL
PlateletWorks (Helena Laboratories, Beaumont , TX
(Excerpts from Cardiopulmonary bypass Edited by Sunit Ghosh, Florian Falter and David Cook. 1st edition. Cambridge University Press, New York
Another reference:
Vig, S. et al. Thromboelastography: a reliable test? (Blood, Coagulation and Fibrinolysis 2001;12:555-61)
Storage of sample over 90 min, showed an instability for 30 min. But, after those 30 minutes, the results were reproducible. Therefore, TEG requires a formal operating procedures established for each institution to be consistent.
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