Factor Assays

Factor VIII Inhibitor?

From Deborah Whetzel, Children’s Hospital of the King’s Daughters, Norfolk, VA: We’ve had a couple patients lately that demonstrated inhibition but their factor VIII results are within normal limits or even elevated. The result values differ 30–40% typically between dilutions but as they’re diluted more, the values go up to 300 or 400%. FVIII values that high […]

Bleeding Disorders

“Backwards” FVIII Dilutions

From Kim Kinney, Indiana University Health, Hi George! We have a severe hemophiliac with an 8BU inhibitor receiving ReFacto. Factor assays are high, but dilutions dilute backward! 367, 238, then 183, then 167 causing a CV flag. We have seen this before, but have never heard an explanation for the “backward” dilution affect. Can you shed light? […]

Coagulation Factors

Antibodies to Bovine Thrombin

From Manju Bala, St Christopher’s Hospital for Children. Need help with interpreting a coagulation dilemma. A child, 4 months old, post cardiac surgery, no meds, use of bovine thrombin during surgery with prolonged prothrombin time (PT), 29.9s; partial thromboplastin time (PTT, APTT),107.7s; and thrombin time (TT), 40.4s; no correction on mixing. FII, 25%; FV, 7%, increasing with […]

Coagulation Factors

FVIII Inhibitor Assays

From Saravanan Vinayagam: We are trying to set up the factor VIII inhibitor assay on our ACL TOP analysers. Has anyone got an SOP or previous experience in validating inhibitor assay in an automated analysers? Thank you. Hello, Saravanan Vinayagam, and thank you for your post. I’m hoping that an IL technical representative will see this […]

Bleeding Disorders

More on Factor Assays and Inhibitors

Here is an in-depth response from Russell Higgins, MD, a colleague of John Olson, MD, and current chair of the Coagulation Resource Committee of the College of American Pathologists (CAP) to Dee McMichael’s March 2 question about monitoring factor activity in the presence of an inhibitor: From Dr; Olson: “We discussed this at our weekly coagulation consensus conference this […]

Factor Assays and Inhibitors

From Dee McMichael, Blood Bank Supervisor, All Children’s Hospital, St. Petersburg, FL: I was trying to post a question on your site but each time I received a connection failure. I will follow up with my IT department but thought I might be able to post my question in an email. (Dee, we apologize for the connection […]

Fitzgerald Factor Assay

There is a helpful new “mdredjka” comment appended to our April 7, 2010 discussion on Fitzgerald Factor assays that was started by Peter Clement, then a student at Brigham Young University. Please take a look!

Comparison of INR with FII, FVIII, and FX

From Dave McGlasson: George, Here is a potential answer for Kelly Townsend’s February 13 post, Factor II Assay in place of INR. Kelly is right. We did look at the chromogenic factor X and published that work a few years ago McGlasson DL, Romick BG, Rubal BL. Comparison of a chromogenic factor X assay with international normalized ratio […]

Anticoagulant Therapy

More on FVIII Linearity

I spoke with Patti Tichenor, UAB special coagulation laboratory who had discussed our December 5, 2012 factor VIII linearity question from Mahnaz Sairi with her UAB colleague Laura Taylor. UAB uses high-end coagulometers (Stago STA-R) for their factor assays, and their linearity extends from near zero to 100%. When they anticipate especially high factor VIII levels, they will order dilutions to as high […]

Factor Assays: How to Define Parallel Results

From Maria Franco, Orlando Health: Hi, George, when running factor assays (1:10, 1:20, etc), is the agreement between results to r/o inhibitory activity all calculated from the original result (1:10)? Not sure what the most common or recommended practice is. I have heard to find the mean of all results and then try to calculate the deviation. […]

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George Fritsma is a medical laboratory scientist, educator, and author. George is a member of the International Society on Thrombosis and Hemostasis, the International Society for Laboratory Hematology, and the American Society for Clinical Laboratory Science.

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