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Factor VIII Inhibitor Assay

A question from Bruce King at Lancaster General:

I was wondering about the practicality of adding a test for factor VIII inhibitors in our community hospital setting. Although we don’t get many requests for it, it appears that when you get a request for a factor VIII inhibitor in a non-hemophilia patient, there is a significant degree of urgency in getting rapid results. Our current reference laboratory performing this test has a TAT of about a week which is less than ideal for a more urgent clinical need for this information. We currently do some more manual coagulation methods such as inhibitor screens with 50:50 mixes and incubation phases. Are there community hospitals doing this test and how did you go about setting it up and running it? Any assistance is most appreciated.

Hi, Bruce. Just a general word on factor VIII inhibitor testing for both hereditary and acquired hemophilia . Besides the Bethesda titer, we have two ways to screen for an inhibitor. You are already using mixing studies with incubation, that is definitive. The second is to watch for non-parallel results when your automated system performs the factor assay at three or more dilutions. Both are qualitative and are usually available at acute care facilities, and while the titer is necessary as a quantitative follow-up, some therapeutic decisions can be made right away.

The Bethesda titer is complex and time-consuming, though it can be mastered by any well-trained clinical laboratory scientist. Most acute care facilities choose to send out their titers because it is a low-volume assay and not very cost-effective to run in-house. Reference labs should be able to turn out a result within 24 hours. If your reference lab has a longer turn-around time, investigate using a local tertiary care facility such as a nearby university hospital. For instance, at University of Alabama at Birmingham Hospital we provide reference services for all the local facilities in northern Alabama.

Let’s see what other Fritsma Factor members suggest. Geo

Comments (2)
Feb 28, 2009 6:08am

George is correct, this is a time consuming procedure. We ma
George is correct, this is a time consuming procedure. We make up for the cost by charging for however many Fx VIII assays we do. You also need a level head to figure out the calculations which can be tough with some coag guy from Chapel Hill hanging over you!

Sue Osier
Northside Hospital Atlanta

Feb 27, 2009 6:14am

Hi George: There would also appear to be some ELISA-based as
Hi George: There would also appear to be some ELISA-based assays available “For Research Use” to qualitatively detect antibodies directed toward recombinant human FVIII. (e.g. Enjoying FF very much… keep up the great work. — Steve

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