Watson C, Kitchen S, Woolley A M, Young L, Malia R G
Sheffield Haemophilia and Thrombosis Centre, Royal Hallamshire Hospital, UK.
Br J Biomed Sci. 1999;56(2):123-7.
The international normalised ratio (INR)/international sensitivity index (ISI) system is established for calibration of thromboplastins for laboratory monitoring of oral anticoagulant therapy. The calibration procedure employs patients stabilised on oral anticoagulants, and is therefore validated for patients within the therapeutic range. For practical reasons, the system is used for patients at all levels of therapy, including over-anticoagulated patients with particularly low levels of factors II, VII and X. We studied patients within and above the therapeutic range, using a thromboplastin containing recombinant human tissue factor (Innovin) and two tissue extract thromboplastins. In samples with INRs from 2.0 to 4.0, there was good agreement between results obtained with the three systems (mean INRs within 4% of each other). In patients with INRs > 4.0, results with a human placental extract reagent (Thromborel S) were similar to those obtained with a rabbit brain thromboplastin (IL PT Fib Hs Plus); mean INRs were 6.30 and 6.32 respectively (not significant). Results with Innovin (mean INR: 7.67) were significantly (P < 0.001) greater (on average by 22%) than those obtained with the other two materials. The discrepancy between results with different reagents negatively correlated with factor VII levels. Thus, the lower the factor VII level, the greater was the discrepancy between INRs. Unexpectedly, there was a positive correlation between factor V level and the difference between INRs with different reagents. Thus, the higher the factor V level, the greater was the discrepancy between INRs. The effect of these differences at higher INRs on patient management is unknown, but the recently revised UK guidelines recommend that management of these patients should be influenced by clinical factors, reducing the relative importance of discrepancies between results obtained with different systems.
国际标准化比值（INR）/国际敏感指数（ISI）系统是为校准用于口服抗凝治疗实验室监测的凝血活酶而建立的。校准程序采用口服抗凝剂稳定的患者，因此在治疗范围内的患者中得到了验证。出于实际原因，该系统用于所有治疗水平的患者，包括抗凝过度且因子II、VII和X水平特别低的患者。我们使用含重组人组织因子的凝血活酶（Innovin）和两种组织提取物凝血活酶，研究了治疗范围内和高于治疗范围的患者。在INR为2.0至4.0的样本中，三种系统获得的结果之间具有良好的一致性（平均INR相互之间相差在4%以内）。在INR>4.0的患者中，人胎盘提取物试剂（Thromborel S）的结果与兔脑凝血活酶（IL PT Fib Hs Plus）的结果相似；平均INR分别为6.30和6.32（无显著差异）。Innovin的结果（平均INR：7.67）显著高于（P<0.001）其他两种材料的结果（平均高22%）。不同试剂结果之间的差异与因子VII水平呈负相关。因此，因子VII水平越低，INR之间的差异越大。出乎意料的是，因子V水平与不同试剂的INR差异之间呈正相关。因此，因子V水平越高，INR之间的差异越大。这些在较高INR时的差异对患者管理的影响尚不清楚，但最近修订的英国指南建议，这些患者的管理应受临床因素影响，降低不同系统获得的结果之间差异的相对重要性。
