From Shaun Seth: I was reading the commentary Dave McGlasson gave regarding the factor X assay and its role in antiphospholipid antibody syndrome. I was curious to know when or why a lab would use the factor II assay vs. the factor X assay.
Hello Shaun and thank you for your question. The factor X chromogenic assay is an excellent means for monitoring warfarin (oral anticoagulant therapy) in place of the PT/INR whenever you suspect interference, such as prolongation by lupus anticoagulant. In theory, a chromogenic factor II (prothrombin) should work just as well, so I contactedMr. McGlasson, who said there just aren’t many stable reliable chromogenic factor II assays available, in contrast to the chromogenic X, which has excellent precision characteristics. I hope this helps. Geo.