ACTIVATED PROTEIN-C RESISTANCE IN PATIENTS WITH ANTI-BETA(2)-GLYCOPROTEIN-I ANTIBODIES

To evaluate if the presence of anti-beta(2)GPI antibodies (a beta(2)GP I) is associated with activated protein C resistance (APC-R) phenotype , we performed the APC-R APTT-based assay in 74 plasma samples from pa tients with antiphospholipid antibodies (aPL). Samples were diluted 1: 5 in factor V-deficient plasma. Lupus anticoagulant (LA), anticardioli pin antibodies (aCL) and a beta(2)GPI (IgG and (IgM) were also perform ed. A control group of 22 healthy volunteers was used. The prevalence of reduced APC-R ratio in patients with aPL was significantly higher t han in normal controls (31.1 vs 4.5%, P < 0.05) and the mean APC-R rat io was lower (mean +/- SD; 2.32 +/- 0.40 vs 2.55 +/- 0.21, P < 0.02). There were no differences in the prevalence of APC-R and the ratio val ues between LA(+) and LA(-). Among the LA(+), the aCL(+) had a higher prevalence of APC-R than the aCL(-) (P < 0.01) and lower APC-R ratios (P < 0.01). The latter group was no different to normal controls. Anti -beta(2)GPI antibodies were associated with a higher prevalence of APC -R (50.0 vs 19.6%, P < 0.001), and lower APC-R ratios (2.15 +/- 0.41 v s 2.42 +/- 0.35, P < 0.005), compared with a beta(2)GPI(-). In conclus ion, the acquired APC-R in patients with aPL seems to be associated wi th aCL and a beta(2)GPI rather than an in vitro interference by LA.