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Factor V Antigen Assay?

From Heather DeVries, Indiana University. Hello George! We have a physician requesting a factor V antigen assay. I have not been able to find it anywhere.  Do you know if there is an assay for this?  If so, who performs it? Thanks! Heather.

Hi, Heather. I checked the usual specialty reference labs and the companies who make niche products, and find no reference to a factor V antigen assay. Given your experience, I’m certain you’ve already checked with the physician to ensure she doesn’t mean the factor V Leiden mutation assay. This ordering issue seems to arise daily in large hemostasis laboratories. Meanwhile, perhaps one of our participants knows of a source for a factor V immunoassay.

Added April 24, 2016: Ali Sadeghi-Khomami, PhD, lead scientist at Precision BioLogic Inc., has located a factor V antigen assay produce by Hypen BioMed and marketed in North America by Aniara. Below see a comment by Dr. Emmanuel Favaloro describing the relative value (or lack thereof) of the factor V antigen test.

Comments (1)
Bleeding Disorders
Apr 23, 2016 5:15pm

I would actually clarify the
I would actually clarify the need to perform a factor V antigen assay before seeking a provider of same. Most factor V requests are inappropriate and the doctor actually wants a factor V Leiden assay (meaning the genetic test or perhaps activated protein C resistance if a clot based assay is preferred). I can think of no highly motivational reason for doing a factor V antigen assay, since the factor V clotting assay will identify any factor V deficient patients. Although there are type 2 variants, with lower activity than antigen, these are rare and the activity level is more important. If this is a follow-up investigation to a low FV activity assay result, then maybe doing a factor VIII assay may be more important (to exclude a combined FV/FVIII defect instead). Suggested reference: Asselta R, Peyvandi F. Factor V deficiency. Semin Thromb Hemost. 2009;35:382–9.

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