Department of Thrombosis and Hemostasis, Leiden University Medical Center, The Netherlands.
Am J Clin Pathol. 2012 Aug;138(2):248-54. doi: 10.1309/AJCPGSB5YPJRREEV.
International normalized ratio (INR) discrepancies were noted between clinical laboratories using various prothrombin time (PT) systems. We studied the influence of different commercial blood collection tubes and different PT systems on INR measurements. INRs of fresh patient samples were determined by 3 laboratories, each using different PT systems. In the first part of the study, samples were drawn with Vacutainer tubes and in the second part with Monovette tubes. In the first part of the study, the maximum bias for all patients amounted to 0.46 INR (14%), and in the second part, to 0.14 INR (4.9%). The maximum bias for all patients could be reduced further by local system calibration using frozen pooled plasma specimens. The sodium citrate solutions in the blood collection tubes were contaminated with magnesium ions (approximately 2.7 mmol/L and 0.3 mmol/L in the Vacutainer and Monovette, respectively). INR discrepancies could be explained largely by this influence of blood collection tubes. The maximum allowable magnesium contamination in sodium citrate anticoagulant solutions should be less than 1 mmol/L.
国际标准化比值（INR）在使用不同凝血酶原时间（PT）系统的临床实验室之间存在差异。我们研究了不同商业采血管和不同 PT 系统对 INR 测量的影响。3 家实验室分别使用不同的 PT 系统，对新鲜患者样本的 INR 进行了测定。在研究的第一部分，使用 Vacutainer 管采集样本，在第二部分使用 Monovette 管采集样本。在研究的第一部分，所有患者的最大偏差达到 0.46 INR（14%），在第二部分达到 0.14 INR（4.9%）。通过使用冷冻混合血浆标本进行本地系统校准，可以进一步降低所有患者的最大偏差。采血管中的柠檬酸钠溶液中被镁离子污染（分别约为 2.7mmol/L 和 0.3mmol/L）。采血管对 INR 差异的影响可以很大程度上得到解释。柠檬酸钠抗凝溶液中允许的最大镁污染应小于 1mmol/L。
