Anonymous asked in Science & MathematicsMedicine · 1 month ago

Why is PTT used to monitor unfractionated heparin when it deals with the extrinsic pathway and not common clotting pathway? ?

2 Answers

  • Anonymous
    1 month ago

    @lab guy 

    The common pathway incorporates both Xa in the intrinsic and extrinsic pathway. It is the last pathway for both the intrinsic and extrinsic pathway. Please look at pictures. 

    Attachment image
  • 1 month ago

    "Heparin inhibits reactions that lead to the clotting of blood and the formation of fibrin clots both in vitro and in vivo. Small amounts of heparin in combination with antithrombin III, a heparin cofactor,) can inhibit thrombosis by inactivating Factor Xa and thrombin."

    PTT incorporates factor Xa in its pathway where as PT does not. 

    PTT reagents are picked selectively for their sensitivity to Factor X which provides a more reliable linearity for dosing purposes. A PTT reagent is said to have a poor or a good sensitivity curve when dealing with various heparin concentrations. Brain and lung are two different sources for PTT reagents which also incorporate activators and so the test is more appropriately called the aPTT or activated PTT test. All of it is to provide sensitivity to heparin.

    Some people also use another reagent PTT that is better for detecting lupus anticoagulant rather than heparin. Two different options for two different situations. 

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