Screening Assays

Factor V Inhibitor

I [Geo] am preparing an audio PowerPoint module describing the primary coagulation assays, PT, PTT, TT, and fibrinogen [Fg] assays. I asked several colleagues if we continue to encounter factor V inhibitors. Before ~2010 we encountered anti-FV and sometimes anti-FV plus anti-FII [prothrombin] as cross-reacting antibodies that arose in response to bovine thrombin used in […]

Screening Assays

New Fundamentals in Hemostasis

Thanks to my colleague Carlo Ledesma, MS, SH(ASCP)QLS, MT(ASCPi), MT(AMT) for pointing me to an in-depth hemostasis review, Versteeg HH, Heemskerk JWM, Levi M, Reitsma PH. New Fundamentals in Hemostasis. Physiol Rev 2013;93:327–58. This is a valuable teaching resource that helps elucidate the cell-based hemostasis model.

Arterial Thrombosis

PT/PTT Screening

Yesterday, 9-1-20, a colleague contacted George [me] because her physcian had ordered a PT and PTT as part of a pre-procedural workup. She asked what the PT/PTT accomplished, and both the physician and nurse practitioner offered no explanation. After considerable discussion, the PT/PTT order was canceled. I recalled a similar situation from 2011 when my […]

Screening Assays

November, 2019 Quick Question

Our November, 2019 Quick Question asked, “What may you substitute for the PT when LAC prolongs the PT?” We accumulated 53 votes. A. None, use the PT anyway: 9% (5) B. Chromogenic anti-Xa: 13% (7) C. Chromogenic factor X: 30% (16) D. Activated clotting time: 8% (4) E. Thrombin time: 11% (6) F. There is […]

Anticoagulant Therapy

Using the PTT After Cardiac Catheterization

From Lori Leppert: I saw a previous post from April 9, 2014 regarding the use of the PTT result as a guide to pulling a sheath. Do you know of any references that we can refer to that indicate the PTT level in which it would be safe to pull the sheath? See the comment […]

Screening Assays

More about Fibrinogen Effect on PT and PTT

Please refer to our January 22, 2018 discussion entitled Effect of Fibrinogen on PT and PTT, and especially to the recent comment from “Anders.” Please help Anders and our parcipants find authority for the comment, “In both the PT/INR and PTT pathways, fibrinogen is seldom the limiting factor. The functional fibrinogen level must be below […]

Screening Assays

Hemophilia B and Extended Half-life Concentrates

Here is another note from Paul Riley, PhD examining the effects of extended half-life factor IX concentrates. on hemophilia B testing. Hemophilia B1: Therapy Classes and Monitoring Factor IX Inhibitor? Y/N Y/N Prophylaxis Conventional half-life recombinant or plasma-derived FIX Extended half-life FIX Preferred assay to measure FIX activity OSA2 (or CSA) CSA (or OSA) 1. […]

Bleeding Disorders

More on HemLibra

I follow-up to our October 6, 2018 post describing emicizumab (HemLibra), I have correspondence dated 9/10/18 from Paul Riley, PhD, MBA, Stago Scientific Business Development Manager for North America. Paul writes, “I was wondering if you should put something on FF about emicizumab, like a survey to find out how people are dealing with it […]

Bleeding Disorders

Effect of Fibrinogen on PT and PTT

From Alan Neal, Pathlab, NZ. Just wanted a private conversation about the January 11, 2018 Fritsma Factor entry, “POC and Plasma-Based PT/INRs.” I do not agree with the comments made within this article and challenge the logic used. Essentially, if monitoring an enzymatic pathway such as coagulation, with the ‘detector’ being used is fibrinogen to […]

Global Hemostasis Assays

PTT and C-reactive Protein

From Dean Willett, Precision BioLogic Inc. As I read the 11-8-17 comments from Dr. Elman a bit of a lightbulb went off in my head. I’m sure you’ve seen the various publications that demonstrate the effect of C reactive protein (CRP) on APTT assays. Here are: https://www.ncbi.nlm.nih.gov/pubmed/22224499; and https://biblio.ugent.be/publication/5838447/file/6839536. There have been some proficiency samples […]

Lupus Anticoagulant

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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

Quick Question