In what scenarios do you use a chromogenic factor X assay in adjusting INR goals for patients on warfarin?

I do not use this method. It has been suggested that such assays be used in patients with lupus-type inhibitors who have significantly prolonged prothrombin times at baseline. In this setting, if the INR is "therapeutic," one would confirm an adequate warfarin effect if the factor X activity was in ...

I also do not use this method, although, as noted below, it has been described in cases of lupus anticoagulant with baseline INR prolongation.