Coagulation Disorders Unit, Department of Medicine, Hematology and HUSLAB Laboratory Services, Clinical Chemistry, Helsinki University Central Hospital, Helsinki, Finland.
Haemophilia. 2011 Sep;17(5):743-51. doi: 10.1111/j.1365-2516.2011.02601.x. Epub 2011 Jun 20.
Haemophilia A replacement therapy is dosed according to patient's weight and plasma FVIII activity (FVIII:C). The FVIII interacts with platelet membrane but limited data on the impact of platelet procoagulant activity (PCA) are available in haemophilia A. Our aim was to characterize individual PCA in vitro in 20 adult haemophilia A patients at various FVIII:C levels. We detected thrombin generation in platelet-poor (PPP) and platelet-rich plasma (PRP) using: (i) calibrated automated thrombography (CAT) triggered with tissue factor, (ii) adhesion-induced PCA upon collagen and (iii) annexin V binding, expression of P-selectin and active glycoprotein (GP) IIbIIIa on platelets after stimulation of GPVI with collagen-related peptide. The FVIII:C levels varied between <1% and 37%. Thrombin generation was individual and strongly enforced by platelets and associated within the three methods. Range of thrombin generation was maximal (up to 30-fold) at FVIII:C levels 1-5%, underlining the impact of platelets in the presence of traces of replacement therapy. At FVIII:C > 5% platelet contribution in the variance faded. Platelet PCA and P-selectin exposure lead to a fivefold variation. Intriguingly, at FVIII:C < 1% thrombin generation in PPP associated negatively with platelet GPVI activation, suggestive of a regulatory interplay between plasma and platelets. In haemophilia A, the variability in thrombin generation is partially related to plasma FVIII:C, but mainly dependent on platelet procoagulant capacity. Annexin V binding and PCA in response to activation by collagen receptors contribute to this variability. In all, platelet PCA at least following collagen interaction significantly impacts thrombin generation in haemophilia A.
血友病 A 的替代疗法是根据患者的体重和血浆 FVIII 活性（FVIII:C）来给药的。FVIII 与血小板膜相互作用，但关于血友病 A 中血小板促凝活性（PCA）的影响的数据有限。我们的目的是在不同 FVIII:C 水平的 20 名成年血友病 A 患者中体外表征个体 PCA。我们使用以下方法在血小板贫乏（PPP）和富含血小板的血浆（PRP）中检测凝血酶生成：（i）用组织因子触发校准的自动血栓形成（CAT），（ii）在胶原蛋白诱导的粘附时的 PCA，以及（iii）在用胶原蛋白相关肽刺激 GPVI 后，血小板上的 Annexin V 结合、P-选择素表达和活性糖蛋白（GP）IIbIIIa。FVIII:C 水平在 <1%至 37%之间变化。凝血酶生成是个体的，并且受到血小板的强烈影响，并与这三种方法相关。在 FVIII:C 水平为 1-5%时，凝血酶生成的范围最大（高达 30 倍），这强调了在存在痕量替代疗法的情况下血小板的影响。在 FVIII:C > 5%时，血小板对变异的贡献消失。血小板 PCA 和 P-选择素暴露导致五倍的变化。有趣的是，在 FVIII:C < 1%时，PPP 中的凝血酶生成与血小板 GPVI 激活呈负相关，这表明在血浆和血小板之间存在调节相互作用。在血友病 A 中，凝血酶生成的变异性部分与血浆 FVIII:C 相关，但主要取决于血小板促凝能力。对胶原蛋白受体激活的 Annexin V 结合和 PCA 有助于这种变异性。总之，至少在与胶原蛋白相互作用后，血小板 PCA 会显著影响血友病 A 中的凝血酶生成。
