Evaluation of abnormal coagulation times (PT and/or aPTT)

This algorithm assumes a normal platelet count has been documented; additional evaluation may be appropriate for individuals with abnormal clotting times plus thrombocytopenia. For individuals with bleeding or thrombosis, the evaluation is similar, but some testing may need to be done simultaneously rather than sequentially, and some tests may be omitted. In addition, therapeutic interventions may be used to treat bleeding or thrombosis while the evaluation is ongoing (at times, before the cause of bleeding or thrombosis has been determined). Refer to UpToDate for further information on the details of these coagulation tests and patient management.

PT: prothrombin time; aPTT: activated partial thromboplastin time; DIC: disseminated intravascular coagulation; TT: thrombin time; FVII: factor VII; RT: reptilase time; VWD: von Willebrand disease.
* Additional testing may include the following:

Testing based on inhibitor characteristics:
- If delayed appearance of inhibitor (2 hours > 5 minutes), check factor VIII activity level
- If immediate appearance of inhibitor (2 hours = 5 minutes), check factor VIII, IX, and XI activity
- If inhibitor corrects with phospholipid addition, additional antiphospholipid antibody testing
Testing for intrinsic pathway defects:
- VWD testing (refer to UpToDate content on VWD)
- Factor VIII, IX, and XI testing
- If these are normal, factor XII testing
Testing for fibrinogen disorders: Refer to UpToDate content on fibrinogen disorders
Testing for common pathway defects:
- Mixing studies with the PT and aPTT
- Factor X, V, and II (prothrombin) activity testing
- Trial of vitamin K supplementation

Graphic 103926 Version 6.0

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Evaluation of abnormal coagulation times (PT and/or aPTT)