From the Guidelines
Protein C levels should be measured at least 48 to 72 hours after stopping Warfarin therapy. To get an accurate Protein C level:
- Discontinue warfarin completely
- Wait 48 to 72 hours
- Obtain a blood sample for Protein C testing This waiting period is necessary because warfarin inhibits production of several proteins involved in the coagulation cascade, including Protein C, and it takes time for the body to restore normal levels after stopping the medication, as stated in the 2014 AHA/ACC guideline for the management of patients with valvular heart disease 1. If testing is done too soon after stopping warfarin, the results may be falsely low, potentially leading to misdiagnosis of Protein C deficiency. Waiting the full 48 to 72 hours ensures that the warfarin's effects have completely worn off and the test reflects the patient's true baseline Protein C level. For patients who require continued anticoagulation, they may be bridged with a different anticoagulant during this period, as it does not affect Protein C levels. It is crucial to note that the anticoagulant effect persists until adequate levels of these proteins are achieved after stopping warfarin therapy, a process that takes at least 48 to 72 hours, as mentioned in the guideline 1.
From the Research
Protein C Levels After Stopping Warfarin
- Protein C levels should be measured at least 14 days after stopping warfarin, as evidenced by a study published in 2010 2.
- This study found that protein C and protein S levels can be determined during the acute phase of venous thromboembolism, and normal results can effectively rule out deficiency with only one test.
- The study also suggested that abnormal results need to be confirmed with repeat testing at a later date, at least 14 days after stopping anticoagulation therapy.
- Another study published in 2017 found that protein C levels remained above baseline levels after restarting warfarin, even with loading doses 3.
- However, it is essential to note that the optimal timing for measuring protein C levels after stopping warfarin may vary depending on individual patient factors and clinical circumstances.
Clinical Considerations
- Patients with protein C deficiency are at increased risk of venous thromboembolism, and measuring protein C levels is crucial in diagnosing and managing this condition 4, 5.
- Warfarin-induced skin necrosis is a rare but potentially life-threatening complication associated with acquired protein C deficiency 6.
- The management of patients with protein C deficiency requires careful consideration of anticoagulation therapy, including the use of warfarin and other anticoagulants 4, 5, 3.