[Comparison of three reactants for the detection of activated protein C resistance due to mutation of factor V Leiden...

The presence of the R506Q mutation of the factor V gene is associated with an increased risk of thromboembolism, particularly during pregnancy. Recently, its involvement in the development of obstetrical complications, such as preeclampsia and fetal losses, has been evoked. The resulting factor VQ506 (factor V Leiden) has arginine 506 replaced by glutamine at the factor Va cleavage site for activated protein C (APC) which induces APC-resistance. During pregnancy, an acquired resistance to APC is observed without the presence of the factor V Leiden mutation which leads to an inappropriate realization of the more expensive DNA analysis. This resistance is at least partly explained by an increase of the factor VIII. In this study, we have compared three reagents: the original test Coatest APC Resistance (Chromogenix) and two modified tests using factor V depleted plasma: Coatest APC Resistance V (Chromogenix) and Accélérimat (BioMérieux). The last test is not influenced by the factor VIII by the adjunction of activated factor X. For each test, the coefficient of discrimination, between carrier and non-carrier of the R506Q mutation of the factor V gene, has been determined on 43 pregnant women (33 non-carriers and 11 heterozygotes) and 51 unselected non pregnant patients with clinically suspected thrombosis (40 non-carriers and 11 heterozygotes). The predilution of the patient's plasma with factor V deficient plasma (Coatest APC Resistance V and Accélérimat) enhances the discrimination between carriers and non-carriers in both groups. However, using Coatest APC Resistance V, a significant difference of results is observed between the two populations in the non-carriers patients. Thus, Accelerimat is probably more efficient than Coatest APC Resistance for the detection of the factor VQ506 during pregnancy.