Thrombin Time
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Thrombin time is a screening coagulation test designed to assess fibrin formation from fibrinogen in plasma.
The reference range for the thrombin time is usually less than 20 seconds (ie, 15-19 seconds), but this depends on the test kit/instrumentation used in the laboratory. Healthy infants up to age 6 months may have a slightly prolonged thrombin time by 2-3 seconds.
A normal thrombin time excludes abnormalities in the fibrin formation process of the coagulation cascade.
A shortened thrombin time is rare and is observed in patients treated with dextran or hydroxyethyl starch or in individuals with certain forms of hereditary dysfibrinogenemia. [1]
A prolonged thrombin time indicates a fibrinogen abnormality, impairment of fibrin formation, and/or a thrombin inhibitory effect.
Fibrinogen abnormalities include the following:
Severe hypofibrinogenemia (fibrinogen level < 0.7-1 g/L) or afibrinogenemia (congenital or acquired)
Congenital or acquired dysfibrinogenemia [1]
Extreme hyperfibrinogenemia (fibrinogen >14 g/L), [2] but not mild fibrinogen elevation due to the acute phase response [3]
Impairments of fibrin formation include the following:
Disseminated intravascular coagulation (presence of fibrin degradation products, D-dimer)
Abnormal circulating proteins due to amyloidosis or multiple myeloma
Thrombin inhibitory effects include the following:
Heparin, hirudin, and direct thrombin inhibitors
Circulating antibodies to thrombin
Specimen: Citrated plasma
Collection: Blue-top tube with 3.2% sodium citrate
Centrifugation: 2000-2500 g for 15 minutes or similar regimen to produce platelet-poor plasma
Storage: Up to 8 hours at room temperature (samples with heparin up to 2 hours); plasma sample should be frozen within 1-2 hours; specimen is stable for one month at -20°C, or 6-9 months at -80°C
Thrombin time is a screening coagulation test designed to assess fibrin formation from fibrinogen in plasma. Thrombin time is performed as the next step in the evaluation of abnormally prolonged activated partial thromboplastin time (aPTT) or prothrombin time (PT). [4]
The thrombin time is used to assess unexplained prolongation of PT or PTT (often with conjunction with reptilase time).
The thrombin time is very sensitive to unfractionated heparin (≥0.05 U/mL) and might be used for detection of accidental heparin contamination of a plasma specimen.
Low albumin levels (< 30 g/L) in the plasma sample can cause thrombin time prolongation due to delayed fibrin polymerization. [5]
Cunningham MT, Brandt JT, Laposata M, Olson JD. Laboratory diagnosis of dysfibrinogenemia. Arch Pathol Lab Med. 2002 Apr. 126(4):499-505. [Medline].
Zhao X, Wang Z, Cao L, Zhang W, Bai X, Dong N, et al. Hyperfibrinogenemia and prolonged clotting times in a Turner syndrome patient with hepatocellular carcinoma. Blood Coagul Fibrinolysis. 2010 Jul. 21(5):398-405. [Medline].
Van Cott EM, Smith EY, Galanakis DK. Elevated fibrinogen in an acute phase reaction prolongs the reptilase time but typically not the thrombin time. Am J Clin Pathol. 2002 Aug. 118(2):263-8. [Medline]. [Full Text].
Rodgers GM, Lehman CM. Hemostasis Screening Assays. Bennett ST, Lehman CM, Rodgers GM. Laboratory Hemostasis: A Practical Guide for Pathologists. Springer; 2007. 85-101.
Toulon P, Frere E, Bachmeyer C, Candia N, Blanche P, Sereni D. Fibrin polymerization defect in HIV-infected patients–evidence for a critical role of albumin in the prolongation of thrombin and reptilase clotting times. Thromb Haemost. 1995 Mar. 73(3):349-55. [Medline].
Jun Teruya, MD, DSc, FCAP Professor of Pathology and Immunology, Vice Chairman for Education, Professor of Pediatrics, Professor of Medicine, Director, Tranfusion Medicine/Blood Banking Fellowship Program, Head, Division of Baylor Transfusion Medicine, Baylor College of Medicine; Director, Division of Transfusion Medicine and Coagulation, Texas Children’s Hospital
Jun Teruya, MD, DSc, FCAP is a member of the following medical societies: American Association of Blood Banks, American Society for Clinical Pathology, American Society of Hematology, College of American Pathologists, International Society on Thrombosis and Haemostasis, Massachusetts Medical Society
Disclosure: Nothing to disclose.
Vadim Kostousov, MD Research Associate, Transfusion Medicine and Coagulation, Department of Pathology and Immunology, Texas Children’s Hospital, Baylor College of Medicine
Disclosure: Nothing to disclose.
Eric B Staros, MD Associate Professor of Pathology, St Louis University School of Medicine; Director of Clinical Laboratories, Director of Cytopathology, Department of Pathology, St Louis University Hospital
Eric B Staros, MD is a member of the following medical societies: American Medical Association, American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology
Disclosure: Nothing to disclose.
Thrombin Time
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