Factor II Assay in Place of INR?

From Kelly Townsend at TriCore Reference Laboratories: We have several patients in whom the INR does not appear to accurately assess their anticoagulation status. Since we do not have the chromogenic factor X assay on our menu, we’re interested in using the factor II activity assay based on a poster presented at THSNA meeting by the Univ of Minnesota. I believe that Dr. Moll has also spoken on this subject. I’m thinking Dave McGlasson might have done work on it, too. Anyone out there using the factor II activity assay and if so,what therapeutic range are you using and can you point me to some good references for our Pharm D?