Trombineretest

Trombineretest, known in English as thrombin time (TT), is a coagulation assay that measures the time required for plasma to clot after the addition of thrombin. It evaluates the final step of the coagulation cascade—the conversion of fibrinogen to fibrin—and is influenced by fibrinogen concentration and function, as well as by inhibitors of thrombin and by fibrin degradation products.

Procedure and principle: Citrated plasma is typically used with the platelets removed. Exogenous thrombin and calcium are added, and the time to visible clot formation is recorded. Reagents and calibrations vary between laboratories, so reference ranges are reagent-dependent, commonly around 14 to 20 seconds. TT is sensitive to the presence of thrombin inhibitors and to abnormalities of fibrinogen, including dysfibrinogenemia and hypofibrinogenemia.

Interpretation: A prolonged TT suggests problems at the fibrin formation step, such as low or dysfunctional fibrinogen, dysfibrinogenemia, or circulating thrombin inhibitors (for example heparin or direct thrombin inhibitors), or high levels of fibrin degradation products. If heparin contamination is suspected, TT can be affected, and standardized methods or heparin-neutralizing steps may be used to interpret results. A normal TT with a prolonged prothrombin time (PT) or activated partial thromboplastin time (aPTT) may indicate upstream factor deficiencies or other coagulopathies; additional tests, such as fibrinogen assays or mixing studies, are often pursued.

Clinical uses and limitations: TT helps evaluate fibrinogen disorders and suspected dysfibrinogenemia, and can aid in detecting thrombin inhibitors in the sample. However, it is highly reagent-dependent, less standardized than PT or aPTT, and its results must be interpreted in the clinical context alongside other coagulation tests.