Anticoagulant Therapy

April 2025 QQ Results: Measuring Warfarin in LAC Patients

Our April 2025 Quick Question asked, “How do you measure warfarin in a patient with LAC?” The poll drew 47 respondents and was a sequel to our March 2025 question, “How do you test for lupus anticoagulant?” that referenced the ISTH‘s most recent LAC guideline, Devreese KMJ, Bertolaccini ML, Branch DW, et al. An update […]

Quick Question Archive

Chromogenic FX Assay versus PT/INR

Here is an April 1, 2025, “Differential Discussions” webinar hosted by Malissa Norfolk, University of Maine Augusta, and David Cabral, University of Massachusetts Dartmouth. It features my colleague David McGlasson on the subject of “Comparison of the CFX Assay to the INR for Monitoring OAC Therapy.” Thank you to these three hemostasis experts for this […]

Anticoagulant Therapy

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. […]

Lupus Anticoagulant

PT/INR Harmonization

Here is an open-access January 2025 publication that describes an organization-wide PT/INR harmonization effort. Click on the reference to obtain the article: Favaloro EJ, Arunachalam S, Chapman K, Pasalic L. Continued harmonization of the international normalized ratio across a large laboratory network: Evidence of sustained low interlaboratory variation and bias after a change in instrumentation. […]

Anticoagulant Therapy

Lab Monitoring For a Patient Transitioning From DOAC to Heparin

From Jessica Warner, MLS (ASCP)cm Technical Specialist Network Coagulation Service Lab Administration Kettering Health Hi George, Has there been much discussion on what sites are using for lab monitoring for patients transitioning from DOAC to heparin? We have strictly been using anti-Xa for heparin monitoring since 2015. We are a 13-site network with 8 hospitals […]

Anticoagulant Therapy

Reptilase Time

I received this question on 9/14/24: Hello George, Is there any condition where reptilase time is prolonged while thrombin time is normal? My answer is, in a word, no. The thrombin time (TT, or TCT) typically uses 50–100 mg topical human or bovine thrombin, mixed 1:1 with plasma. A normal plasma/thrombin mix clots within ~20 […]

Bleeding Disorders

Prolonged DRVVT Screen

Soha Abuelela asked how to report a DRVVT screen above 120 seconds and how to report the ratio. I [Geo] consulted with my colleague Dave McGlasson. We began by assuming that 120 seconds represents your instrument’s limit and that the actual clotting time was unrecorded. It could be that your specimen has an undetected clot […]

Anticoagulant Therapy

VKA Monitoring in Hepatic Insufficiency

Here is a challenging case from Hrvoje Melinšćak sent 5-30-24: Dear George, In hepatic insufficiency there is often a prolonged basal protime, how to ensure therapeutic values of warfarin when the INR is already elevated? This is of particular concern in those with mechanical cardiac valves. Serum warfarin levels (spectrophotometry) are cumbersome and take days to […]

Establishing the PTT-based UFH Therapeutic Range

A March 22 entry from Robyn Coleman, Senior Scientist, Coagulation, Haematology, Sullivan Nicolaides Pathology, Queensland, Australia: Dear George, I am seeking some direction on APTT therapeutic ranges for UFH. We are facing a change to our APTT reagent. The cohort of patients we would have traditionally used to validate UFH therapeutic range (TR) for APTT, […]

Anticoagulant Therapy

Anti-XI Anticoagulant

Here is a transcript of an interview with Christian T. Ruff, MD, Senior Investigator, Thrombolysis in Myocardial Infarction (TIMI) Study Group, Boston, Massachusetts,USA describing the favorable AZALEA-TIMI Phase 2 safety study of a monoclonal anti-XI once-a-month injectable anti-XI anticoagulant, abelacimab.

Anticoagulant Therapy

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George Fritsma is a medical laboratory scientist, educator, and author. George holds faculty appointments with Rutgers University and Michigan State University, and is a member of the International Society on Thrombosis and Hemostasis, American Association of Clinical Chemists, and American Society for Clinical Laboratory Science.

Cheat Sheets from George

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