Resistance to activated protein C is an anomaly described by Dahlbäck in 1993. Bertina discovered in 1994 the presence of a mutation in the factor V (FV) gene. This mutation leads to the replacement at position 506 of an arginine by a glutamine (Arg506Gln), which affects one of the sites of cleavage of FV by PCa. As a result, FV "resists" inactivation by PCa. The mutated FV is referred to as FV Leiden. This factor V loses its function as a cofactor of the protein C system, that is to say of a system which inhibits coagulation; on the other hand, it retains its procoagulant properties. There are other cases of mutations related to the resistance of activated protein C.
Pefakit® APC-R Factor V Leiden is a functional plasma coagulation test which differs from other functional tests for resistance to APC by acting specifically at the prothrombinase complex level.
Any interference from UFH, LMWH or pentasaccharide in the blood sample is excluded by the addition of polybrene (heparin inhibitor) to reagents 1 and 2. The strength and specificity of the test are enhanced by the elimination of possible disturbances by factors upstream of the coagulation cascade and calcium independence. Results available on different types of analyzers.