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Thrombin time
Last reviewed: 05.07.2025
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Reference values (norm) of thrombin time are 12-16 s.
Thrombin time is the time required for the formation of a fibrin clot in plasma when thrombin is added to it. It depends only on the concentration of fibrinogen and the activity of thrombin inhibitors (ATIII, heparin, paraproteins) and evaluates both phase III of blood coagulation - the formation of fibrin, and the state of natural and pathological anticoagulants.
The determination of thrombin time most often pursues the following goals:
- monitoring of heparin therapy, especially when using high molecular weight heparin;
- monitoring of fibrinolytic therapy;
- diagnosis of hyperfibrinolytic conditions;
- diagnostics of afibrinogenemia and dysfibrinogenemia.
Thrombin time indirectly reflects the concentration of fibrinogen, therefore it is prolonged in hereditary and acquired afibrinogenemia and hypofibrinogenemia (in severe liver damage, fibrinolysis, acute DIC syndrome). Thrombin time is also prolonged in paraproteinemia.
Determination of thrombin time is one of the common methods of monitoring treatment with heparin and fibrinolytics. In these cases, thrombin time should be increased by 2-3 times. When conducting thrombolytic therapy, it is recommended to determine thrombin time every 4 hours, while it should be remembered that if it exceeds the optimal value by more than 2-3 times, then the dose of streptokinase should be increased to increase the consumption of plasminogen and reduce the formation of plasmin; if thrombin time decreases below the optimal value, the dose of streptokinase should be reduced so that part of plasminogen is not blocked in the form of activator, but is completely converted into plasmin.