Some questions about factor VIII inhibitors from Kelly Townsend at TriCore:
When performing Factor VIII inhibitor testing, at what activity level do you either treat the specimen to inactivate patient factor VIII or not perform the assay?
If you do treat the sample, exactly what do you do (what temp and how long)?
Does your protocol differ if the patient has hemophilia and has an inhibitor because he’s been getting product versus a non-hemophilia patient with an acquired inhibitor?
Thanks for any advice you can give,
Kelly Townsend, MT(ASCP)SH
TriCore Reference Laboratories
Hello, Kelly, good to “hear” from you. I checked your question with my colleagues Laura Taylor and Patti Tichenor in the University of Alabama at Birmingham special coagulation laboratory. At UAB we do not perform a Bethesda titer when the factor VIII activity level is above 30%, same for both allo- and autoantibodies. If the factor VIII level is borderline and the factor VIII assay shows non-parallel inter-dilution results, we perform the titer. We don’t inactivate the factor VIII when over 30%. I’ll be interested to see whether other experts inactivate the factor, and what can be accomplished by this step. Geo.