A HIGHLY SPECIFIC FUNCTIONAL TEST FOR FACTOR-V-LEIDEN - A MODIFIED TISSUE FACTOR ASSAY FOR ACTIVATED PROTEIN-C RESISTANCE

We compared the sensitivity and specificity of a tissue factor-based a ssay (FVR) with the addition of a phospholipid/silica preparation, to the commercially available aPTT-based method, APCR (Coatest(TM)), and a modified aPTT-based method (APCM) which utilized factor V-depleted p lasma, for the detection of the factor V Leiden mutation. A total of 1 10 patients were included in this study. This included 32 patients on coumadin therapy, 7 patients on heparin therapy, 5 patients on both an ticoagulants therapy, and 24 patients who were positive for anticardio lipin antibody (ACL) and/or lupus inhibitor (LI), Our data demonstrate that the FVR is not affected by anticoagulation treatment or ACL/LI a ntibodies, whereas in the APCR method, 33 patients cannot be determine d either due to the anticoagulant therapy or presence of the ACL and/o r LI, With the APCM method, the clotting endpoint could not be determi ned in 1 patient due to the presence of a strong LI, The additional ph ospholipid/silica material utilized in the FVR enhanced the APC degrad ation of factor V, and therefore sharpened the demarcation between the factor V Leiden-positive and -negative patients. The sensitivity for the APCR, APCM and EVR was 42, 97 and 100% respectively, The specifici ty for the APCR, APCM and FVR was 94, 96 and 100% respectively.