1Discovery Medicine and Clinical Pharmacology, Bristol-Myers Squibb, Princeton, NJ, USA.
Clin Appl Thromb Hemost. 2013 Sep;19(5):522-8. doi: 10.1177/1076029612441859. Epub 2012 Apr 2.
Conventional prothrombin time (PT) assays have limited sensitivity and dynamic range in monitoring the anticoagulant activity of direct factor Xa inhibitors. Hence, new assays are needed. We modified a PT assay by adding calcium chloride (CaCl2) to the thromboplastin reagent to increase assay dynamic range and improve sensitivity. Effects of calcium and sodium ion concentrations, and sample handling, were evaluated to optimize assay performance. Increasing concentrations of calcium ions produced progressive increases in PT across the factor Xa inhibitor concentrations of 0 to 2500 nmol/L for razaxaban and apixaban. The greatest effect was seen when the thromboplastin reagent was diluted 1:2.25 with 100 mmol/L CaCl2 (thus selected for routine use). The optimized assay showed an interassay precision of 1.5 to 9.3 percentage coefficient of variation (%CV) for razaxaban and 3.1 to 4.6 %CV for apixaban. We conclude that the modified PT assay is likely to be suitable as a pharmacodynamic marker for activity at therapeutic concentrations of factor Xa inhibitors.
传统的凝血酶原时间（PT）检测方法在监测直接因子 Xa 抑制剂的抗凝活性方面灵敏度和动态范围有限。因此，需要新的检测方法。我们通过在凝血酶原试剂中添加氯化钙（CaCl2）来修改 PT 检测方法，以增加检测的动态范围并提高灵敏度。评估了钙离子和钠离子浓度以及样品处理的影响，以优化检测性能。随着钙离子浓度的增加，在 0 至 2500 nmol/L 的 razaxaban 和 apixaban 因子 Xa 抑制剂浓度范围内，PT 呈渐进性增加。当凝血酶原试剂用 100 mmol/L CaCl2 稀释 1:2.25 时，效果最大（因此选择用于常规使用）。优化后的检测方法显示 razaxaban 的批间精密度为 1.5%至 9.3%，apixaban 的批间精密度为 3.1%至 4.6%。我们得出结论，改良的 PT 检测方法可能适合作为因子 Xa 抑制剂治疗浓度下活性的药效学标志物。
