Clotting Screen

Coagulation

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Description

A full clotting screen includes the following tests.

·         Prothrombin Time.

·         Activated Partial Thromboplastin Time.

·         Clauss Fibrinogen.

Prothrombin Time (PT)

The prothrombin time is the time in seconds that it takes plasma to clot after the addition of thromboplastin (tissue factor). Therefore, it depends on the normal function of Factor VII of the extrinsic pathway and the common pathway downstream to it. The prothrombin time can be prolonged by any disease or medication affecting these factors. Warfarin inhibits synthesis of the vitamin K-dependent factors II, VII, IX, and X.

Activated Partial Thromboplastin Time (APTT)

The APTT, a global screening procedure used primarily to evaluate coagulation abnormalities in the intrinsic pathway, will also detect severe functional deficiencies in factors of the common pathway, the effects of unfractionated heparin (see Test Heparin ratio) and to the presence of inhibitors. In patients receiving vitamin K antagonist oral anticoagulants, the circulating levels of factors II, VII, IX and X are reduced, therefore the APTT can be expected to be prolonged. Prolonged clotting times may also be observed in the following situations; deficiency of Factor XII, liver disease and Vitamin K deficiency.

Fibrinogen

Decreased fibrinogen concentration or impaired function can lead to hemorrhage. Thus fibrinogen testing is frequently utilized in the setting of trauma, surgery, disseminated intravascular coagulopathy, and fibrinolytic treatment to determine the need for replacement product. Rarely, congenital decreases in fibrinogen such as congenital hypofibrinogenemia and afibrinogenemia are observed. In addition, qualitative deficiencies in fibrinogen activity (dysfibrinogenemia) may be seen, due either to acquired or congenital causes.

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Sample Type

Plasma (Citrate 2.7ml Blue) x 1

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Reference Range

Adult reference ranges are indicated on the report.

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Turnaround Time

Within 1 hour

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Testing Frequency

Daily/continuous processing 24hrs

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External Notes

NGH/RHH : Combination of screening tests. Includes Prothrombin time, Activated Partial Thromboplastin time and Fibrinogen. Should not be requested for patients on warfarin or Unfractionated heparin.

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Please note: the above information is subject to change and we endeavour to keep this website up to date wherever necessary.