Thromboelastogram (TEG) - Result interpretation

TEG result parameters:
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) – currently, not approved by FDA
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.

1 comment:

Vitali said...

TEG in a nutshell.

R (reaction time) - normal range is 5-10 min. Elevation represents deficient in clotting factors and is treated with FFP.

K (K time) - normal range is 1-3 min. Elevation represents deficient fibrinogen and is treated with CRYOPRECIPITATE.

Alpha angle - normal range is 53-72 degrees. A low value represents deficient fibrinogen and is treated with CRYOPRECIPITATE.

MA (maximum amplitude) - normal range is 50-70 mm. A low value represents deficient platelets and is treated with PLATELETS.

LY30 (lysis at 30 min) - normal range is 0-8%. A higher value indicates excess fibrinolysis and is treated with AMICAR.