Prolonged INR
April 24th, 2019
Overview
Causes of Prolong PT/INR
Isolated Prolonged PT/INR
- Warfarin (low dose)
- Mild vitamin K deficiency
- Factor VII deficiency
Prolonged PT/INR and APTT
- Artefactual - high haematocrit
- Liver disease
- Disseminated intravascular coagulation (DIC)
- Common pathway deficiency - X, V, II, fibrinogen
- Severe vitamin K deficiency
- High dose heparin
- Warfarin
- Factor IIa inhibitors (dabigatran)
- Factor Xa inhibitors (rivaroxaban, apixaban)
Approach
- Determine whether the patient is on warfarin or any other anticoagulants.
- Check the patient's haematocrit, which if elevated will falsely elevate PT/INR and APTT
- Look for evidence of chronic liver disease, either in the patient's past medical history or current clinical state.
- Assess the patient's risk of DIC given their clinical state.
- If unsure about the cause of prolonged PT/INR, mixing studies can be performed.
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