Factor Assays

Modified Nijmegen-Bethesda Assay

Precision BioLogic Inc. presented MNBA data at the World Federation of Hemophilia (WFH) 2018 World Congress in Glasgow, Scotland, May 20–24. Recognizing the need to improve factor VIII (FVIII) inhibitor testing for people with hemophilia A, the company studied the agreement between a chromogenic modified Nijmegen-Bethesda assay (MNBA) and a qualitative ELISA test in the […]

Bleeding Disorders

Nijmegen Bethesda Assay

Dr. Ali Sadeghi-Khomami, Precision BioLogic Inc., provided these in-depth technical questions about the Nijmegen Bethesda Assay (NBA), which we use to quantitate specific factor inhibitors such as anti-factor VIII or anti-factor IX. George forwarded his questions to Connie Miller and Amanda Payne, US Centers for Disease Control and Prevention (CDC) who have been working on […]

Bleeding Disorders

Factor Substitution Assays

George occasionally receives questions about factor substitution assays. We coagulationists of a “certain age” can recall preparing barium sulfate or aluminum hydroxide “adsorbed” plasma, aged plasma, and serum, then performing mixing studies on prolonged PTT patient plasmas. We mixed the patient plasma 1:1 with pooled normal plasma and the adsorbed and aged plasma and serum, […]

Quick Question Results: Bethesda Titers

The results of our latest Quick Question are in with 87 responses.. How does your laboratory measure factor inhibitors? Standard Bethesda assay: 33% (26) Bethesda titer using buffered pH 7.4 pooled normal plasma: 9% (8) Nijmegen Bethesda assay using factor-depelted plasma as diluent: 9% (8) CDC modification of Nimegen Bethesda assay: 0% (0) Bethesda chromogenic […]

Bleeding Disorders

Chilling The NBA Reaction Mixture

From Dr. Mirta Arias: Dear George, Thank you for your answer in the blog. I have another question. Dr. Robinson in ISLH argued that it is good to chill the post 2 hour/37°C 37 incubation mixtures of patient + pool normal plasma, and control at 2–8°C for 10 minutes and then measure the factor VIII. In […]

Bleeding Disorders

Nijmegen Bethesda Assay

From Dr. Mirta Arias, Dear George, which is the procedure for determining the cut-off of Bethesda method and Nijmegen? Is there any Excel spreadsheet to perform it? Do you use only normal or normal and patients? Thanks, Mirta Hello, Dr. Arias, and thank you for your question. For a comprehensive answer, I turned to Amanda […]

Bleeding Disorders

Nijmegen-Bethesda Assay Method

Sarah Payne and Kerri Klemm request information on how to perform the CDC modification of the Nijmegen-Bethesda Assay for coagulation factor inhibitors. Thank both of you for your request, which provides George the opportunity for self-promotion. Please tap or click Coagulation Factor Inhibitors and the Nijmegen Bethesda Assay, a recording of my June 2 digital […]

Bleeding Disorders

Factor Assay Analytical Sensitivity

Debra Goode, Medfusion, sent this message: I do not see methods or data for performing functional sensitivity tests for coagulation assays, particularly clotting factor assays. Is this not done conventionally and if not, why? George confirmed that the inquiry refers to analytical sensitivity of clot-based coagulation factor assays. Debra, thank you, and yes, for each […]

Bleeding Disorders

Mixing Studies and Factor Assays

George is attending the International Society for Laboratory Hematology in Chicago, where he was presented a follow-up mixing studies question that was provoked by excellent discussions led by Drs. Mary Robinson and Dorothy Adcock of Esoterix Coagulation. The questioner performs a 1:1 mixing study using NP, and if it corrects, follows up with a mixing […]

More on Prekallikrein Deficiency

Here is an comment on Tracy Dixon’s prekallikrein deficiency case from Dr. Tom Exner, Haematex, Sydney, Australia. Hi, George, thanks for the interesting case; from Australia of all places! I’ve written up a couple of such cases many years ago. PKK and HMWK-deficient plasmas may be less readily available these days but the antibodies are […]

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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.

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