Department of Anesthesiology, Northwestern University Feinberg School of Medicine, Chicago, Illinois.
Department of Anesthesiology, University of Rochester, Rochester, New York.
Anesth Analg. 2019 Jun;128(6):1089-1096. doi: 10.1213/ANE.0000000000003457.
Patients presenting for surgery may have isolated or combined prolonged activated partial thromboplastin time (aPTT) and/or prothrombin time (PT). In patients not receiving anticoagulants or with no identifiable cause for abnormal clot formation, a mixing study is performed. The index of circulating anticoagulant (ICA) has been used to predict the presence of an inhibitor, usually a lupus anticoagulant.
We retrospectively reviewed the results of mixing studies performed at Northwestern Memorial Hospital, between January 1, 2010 and February 29, 2012. We determined the number of samples that normalized or remained prolonged, the clotting factors associated with prolonged test results, and the presence of coagulation inhibitors. We calculated the ICA in the samples with prolonged aPTT and PT to determine its ability to predict a lupus anticoagulant. The primary comparison of interest was the diagnostic utility of the ICA at cutoff values of 11% for predicting the presence of lupus anticoagulant.
There were 269 mixing studies performed: 131 samples with prolonged aPTT; 95 with prolonged PT; and 43 with both prolonged aPTT and prolonged PT. Of the samples with a prolonged aPTT, 55 of 131 (42%) normalized, 36 of 131 (27%) partially corrected, and 40 of 131 (31%) remained prolonged. Thirty-three of 95 samples (35%) with prolonged PT normalized, while 62 of 95 (65%) remained prolonged. Eight of 43 (19%) mixing studies of patients with prolonged PT and aPTT normalized; the aPTT normalized, but the PT remained prolonged in 17 of 43 (39%); the PT normalized, but the aPTT remained prolonged in 7 of 43 (16%); and both tests remained prolonged in 11 of 43 (26%) samples. Prolongations in the aPTT were primarily associated with low activities of CF XII, while the majority of the prolongations in PT were secondary to low activities in CF VII. Combined prolongations were secondary to deficiencies in both the intrinsic and extrinsic as well as the common pathways. An ICA >11% had 100% (95% CI, 59%-100%) sensitivity, 53% (95% CI, 35%-70%) specificity, and 77% (95% CI, 62%-92%) accuracy in predicting the presence of lupus anticoagulant in patients with prolonged aPTT.
Normalization of the aPTT and PT in a mixing study was associated with low clotting factor activity. The ICA may be helpful in predicting the presence of a lupus anticoagulant. As anesthesiologists take ownership of the perioperative surgical home, we need to understand the clinical implications of the results of mixing studies.
接受手术的患者可能存在孤立或合并的延长活化部分凝血活酶时间（aPTT）和/或凝血酶原时间（PT）。对于未接受抗凝治疗或无明确原因导致异常凝血形成的患者，应进行混合研究。循环抗凝剂指数（ICA）已被用于预测抑制剂的存在，通常是狼疮抗凝剂。
我们回顾性分析了 2010 年 1 月 1 日至 2012 年 2 月 29 日在西北纪念医院进行的混合研究结果。我们确定了正常化或持续延长的样本数量、与延长测试结果相关的凝血因子以及凝血抑制剂的存在。我们计算了延长 aPTT 和 PT 的样本中的 ICA，以确定其预测狼疮抗凝剂的能力。主要比较的是 ICA 在 11%的截断值下预测狼疮抗凝剂存在的诊断效用。
共进行了 269 项混合研究：131 项 aPTT 延长样本；95 项 PT 延长样本；43 项 aPTT 和 PT 均延长样本。在 aPTT 延长的样本中，55/131（42%）正常化，36/131（27%）部分纠正，40/131（31%）持续延长。95 项 PT 延长样本中，33/95（35%）正常化，62/95（65%）持续延长。43 项同时延长 PT 和 aPTT 的患者中，8/43（19%）混合研究正常化；aPTT 正常化，但 17/43（39%）PT 持续延长；PT 正常化，但 7/43（16%）aPTT 持续延长；43 项研究中有 11/43（26%）样本两种检测均持续延长。aPTT 的延长主要与 CF XII 活性降低有关，而大多数 PT 延长与 CF VII 活性降低有关。联合延长与内在、外在和共同途径的双重缺陷有关。ICA>11%时，预测 aPTT 延长患者狼疮抗凝剂存在的敏感性为 100%（95%CI，59%-100%），特异性为 53%（95%CI，35%-70%），准确性为 77%（95%CI，62%-92%）。
混合研究中 aPTT 和 PT 的正常化与凝血因子活性降低有关。ICA 可能有助于预测狼疮抗凝剂的存在。随着麻醉医师对围手术期外科之家的拥有，我们需要了解混合研究结果的临床意义。
