Reptilase Time
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The reference range for reptilase time depends on the test kit or instrumentation used in the laboratory but is usually below 20 seconds (ie, 15-19 seconds). Healthy infants aged 6 months or younger may have a slightly prolonged reptilase time by 2-3 seconds.
Similar to thrombin time (TT) normal reptilase time excludes abnormalities in fibrin formation process of coagulation cascade; however, the test is not sensitive to heparin (low-molecular-weight heparin or unfractionated heparin) or direct antithrombin inhibitors (eg, hirudin, bivalirudin, argatroban, dabigatran).
Normal reptilase time with prolonged TT indicates that the specimen contains drugs or heparinlike molecules with antithrombin activity. [1]
Prolonged reptilase time suggests the following fibrinogen abnormalities:
Severe hypofibrinogenemia or afibrinogenemia (congenital or acquired)
Congenital or acquired dysfibrinogenemia
Moderate hyperfibrinogenemia (>7 g/L) [2]
Reptilase time testing also reveals impairment of fibrin formation, including the following:
Disseminated intravascular coagulation (presence of fibrin degradation products, D-dimer)
Abnormal circulating proteins due to amyloidosis, multiple myeloma
See the list below:
Specimen – Citrated plasma
Collection – Tube with 3.2% sodium citrate, blue top
Centrifugation – 2000-2500 g for 15 minutes or similar regime to produce platelet poor plasma
Storage – 8 hours at room temperature (samples with heparin up to 2 h) or plasma sample should be frozen within 1-2 hours; specimen stable for one month at -20 º C, 6-9 months at -80 º C.
Reptilase time is a specific coagulation test designed to assess fibrin formation from fibrinogen in plasma. Reptilase time is modified TT when thrombin is replaced with enzyme “reptilase” purified from snake venom. Contrast to thrombin, reptilase cleaves only fibrinopeptide A (but not fibrinopeptide B) during fibrin clot formation. Reptilase time testing is performed as next step to evaluate abnormally prolonged activated partial thromboplastin time (PTT) or prothrombin time (PT) with concomitantly prolonged TT. [3, 1]
Unexplained prolongation of PT or PTT with prolonged TT is an indication for testing reptilase time.
Low albumin levels (< 30 g/L) in plasma sample can cause reptilase time prolongation due to delayed fibrin polymerization. [4]
Rodgers GM, Lehman CM. Hemostasis Screening Assays. Bennett ST, Lehman CM, Rodgers GM. Laboratory Hemostasis: A Practical Guide for Pathologists. Springer; 2007. 85-101.
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].
Cunningham MT, Brandt JT, Laposata M, Olson JD. Laboratory diagnosis of dysfibrinogenemia. Arch Pathol Lab Med. 2002 Apr. 126(4):499-505. [Medline].
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].
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.
Reptilase Time
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