April 2025 Quick Question: How to Measure Warfarin in a LAC Patient

Our April 2025 Quick Question is a poll that asks, “How do you measure warfarin in a patient with lupus anticoagulant (LAC)?” This question is a sequel to our March 2025 question, “How do you test for lupus anticoagulant?” that references the ISTH‘s most recent LAC guidelines, Devreese KMJ, Bertolaccini ML, Branch DW, et al. An update on laboratory detection and interpretation of antiphospholipid antibodies for diagnosis of antiphospholipid syndrome: guidance from the ISTH-SSC Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibodies. J Thromb Haemost. 2025;23(2):731-744. doi: 10.1016/j.jtha.2024.10.022. In this question we address the possibility that LAC could factitiously prolong some PT results as it binds reagent phospholipid. Please select your answer from the column on the right and add your comments below.