Related Experiment Video
Updated: Apr 27, 2026

The Nijmegen Hemostasis Assay: Simultaneous Fluorogenic Measurement of Thrombin and Plasmin Generation in a Single Well
Published on: February 27, 2026
Antithrombin levels are unaffected by warfarin use
Michael J Sanfelippo1, Jessica M Engel, Adedayo A Onitilo
1From the Department of Hematology/Coagulation Services, Marshfield Labs, Marshfield (Mr Sanfelippo), the Marshfield Clinic Cancer Care at St Michaels, Stevens Point (Ms Engel), and the Department of Hematology/Oncology, Marshfield Clinic Weston Center, Weston (Dr Onitilo), Wisconsin.
Context:
The results of studies among patients with antithrombin deficiency have suggested that the use of warfarin will increase the level of antithrombin.
Objective:
To reevaluate the effect of warfarin on antithrombin levels using an automated amidolytic method in current use.
Design:
Antithrombin levels were measured in patients who were receiving warfarin for atrial fibrillation and were compared with antithrombin levels in preoperative patients who had not received warfarin.
Results:
Patients receiving warfarin had a mean antithrombin level of 100.40% (range, 81%-153%). Patients not receiving warfarin had a mean antithrombin level of 99.97% (range, 79%-120%). The Student t test was not significant for a difference between the mean antithrombin levels of the 2 populations.
Conclusions:
The use of warfarin does not increase the level of antithrombin in patients receiving the drug.
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