Thrombin Time

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Contents 1 Introduction 2 Clinical-significance 3 Increases 4 More General Terms 5 Additional Terms 6 References

Introduction

• The assay is performed adding exogenous thrombin to citrated plasma & measuring the time to clot formation. Normal value:
• time of control +/- 2 sec when control is 9-13 sec
• time of control +/- 5 sec when control is 15-20 sec

Clinical-significance

• measures late phase of coagulation
• affected by concentrations of fibrinogen & by the presence of fibrin degradation products
• does NOT distinguish disseminated intravascular coagulation ( DIC) from primary fibrinolysis

Increases

• plasma fibrinogen levels < 50 mg/dL or dysfibrinogenemia*
• heparin
• fibrin degradation products ( DIC)
• paraproteinemia
• cirrhosis
  

• * may be associated with frequent or severe bleeding [3]

More General Terms

• clinical coagulation test

Additional Terms

• coagulation cascade

References

1. Clinical Diagnosis & Management by Laboratory Methods, 19th edition, J.B. Henry (ed), W.B. Saunders Co., Philadelphia, PA. 1996, pg 726
2. Guide to Clinical Laboratory Tests, 3rd ed, NW Teitz (ed) WB Saunders, 1995
3. Harrison's Principles of Internal Medicine, 13th ed. Isselbacher et al (eds), McGraw-Hill Inc. NY, 1994, pg 322

thrombin time (TT)