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Quick Question: FVIII Inhibitor Assay Cutoff

Our June Quick Question asked, “Most laboratories perform a FVIII activity assay before starting a Bethesda titer for FVIII inhibitor. At what FVIII activity level do you cancel the order for the titer?

a. 20% activity: 6 respondents, 35%
b. 30% activity: 3 respondents, 18%
c. 40% activity: 1 respondent, 6%
d. 50% activity: 6 respondents, 35%
e. We do the titer anyway: 1 respondent, 6%

This is another area where the coagulation laboratory could profit from developing a consensus. Perhaps we will hear something at the ISTH meeting in Boston July 11-15 to illuminate this question. Geo.

Comments (1)
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Weinberh
Oct 9, 2012 9:46am

Hi George,
Did you hear anything more on this question? Th

Hi George,
Did you hear anything more on this question? This has recently come up in our hemophilia clinic where the MD’s are ordering Factor plus inhibitor assay on every patient every week no matter what the factor level is. Thanks.

Holly Weinberg, St. Luke’s Health System

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