Laboratory control of oral anticoagulant therapy: preservation of prothrombin time specimens using a polypropylene collection system

Previous studies have shown a marked time and temperature dependent shortening of the prothrombin time (PT) when blood is exposed to borosilicate (glass) or siliconized borosilicate tubes. Current recommendations are that samples for PT estimation should be tested within 2 h of collection. In this study using polypropylene collection tubes, blood obtained from 30 patients on oral anticoagulant therapy showed no significant change in International Normalized Ratio (INR) value after 24 h storage - either at 4 à °C or room temperature. After 48 h, changes in INR values from refrigerated samples were still clinically insignificant. After 48 h storage at room temperature, however, a minority of samples showed an increase in INR value which may be of clinical importance. The range of INRs studied was 1.0-9.1. In a second evaluation, replicate specimens from 22 orally anticoagulated patients with INRs ranging from 1.0 to 9.6 showed no significant change after 24 h at either temperature - even when samples had been subjected to 30 min of gentle agitation prior to storage and analysis. Overall, the results indicate that when polypropylene collection tubes are used, prothrombin time specimens can be successfully preserved for up to 24 h at room temperature or up to 48 h when refrigerated.     

Sensitivity of the thrombin clotting time and activated partial thromboplastin time to low level of antithrombin III during heparin therapy

Summary. The thrombin clotting time (TCT) has been used at our institution, along with the activated partial thromboplastin time (aPTT), for monitoring heparin therapy. We have observed that, in some patients, a discrepancy develops between the heparin levels predicted by the TCT and the aPTT with the TCT consistently predicting a lower heparin level than the aPTT. An inverse relationship was noted between the functional antithrombin III (AT-III) level and the magnitude of this discrepancy.     

活化部分凝血活酶时间与急性ST段抬高心肌梗死血栓负荷的相关性

目的探讨急性心肌梗死患者的活化部分凝血活酶时间(aPTT)与冠状动脉内血栓负荷之间的关系。方法收集2011年1月至2013年12月首都医科大学附属北京友谊医院急诊住院的急性ST段抬高心肌梗死(STEMI)患者424例,且均在6 h内接受了直接经皮冠状动脉介入(PCI)治疗。根据冠状动脉造影及介入治疗术中情况,将患者分为高血栓负荷组(199例)和低血栓负荷组(225例)。所有患者均在急诊就诊时测量基线的血液学指标和血栓负荷状态。采用SPSS 19.0统计学软件对数据进行处理,组间多因素分析采用logistic分析。结果高血栓负荷组与低血栓负荷组平均年龄[(59.4±11.7)和(61.9±11.8)岁]、aPTT[(24.9±3.2)和(26.6±4.0) s]、凝血酶原时间(PT)[(11.3±0.8)和(11.5±1.0)s]、左回旋支(LCX)比例[9.5%(19/199)和18.0%(40/225)]、男性比例[84.3%(168/199)和74.3%(167/225)]、白细胞计数[(10.0±3.1)×10~9和(9.3±3.1)×10~9/L]、右冠状动脉(RCA)比例[45.2%(90/199)和29.8%(68/225)]比较,差异均有统计学意义(均P0.05)。2组吸烟状况、用药、既往患有高血压及糖尿病比例、肝肾功能、电解质、PTA、AT-Ⅲ、FBG等指标比较,差异均无统计学意义(均P0.05)。组间多因素logistic分析结果显示,aPTT(OR=1.175,95%CI 1.102～1.252)和RCA(OR=2.783,95%CI 1.409～5.497)为高血栓负荷的独立预测因子(P0.01)。aPTT的受试者工作特征曲线下面积为0.660(95%CI 0.608～0.711,P0.001)。结果提示,排除高血栓负荷的aPTT的最佳临界值为26.05(灵敏度为53.5%,特异度为72.6%)。结论急性ST段抬高型心肌梗死患者急诊就诊时缩短的aPTT值与PCI治疗时所见的高血栓负荷相关。     

Differential diagnosis and clinical management of isolated prolonged activated partial thromboplastin time in a patient with Hashimoto thyroiditis-associated thyroid cancer: A case report

Rationale:Patients preparing for surgery may have isolated, prolonged activated partial thromboplastin time (APTT). Cause analysis is warranted in patients who had neither bleeding symptom nor thromboembolic events because isolated prolongation of APTT may lead to unnecessary delayed surgical intervention or invasive procedure, even ineffective plasma infusion treatments. Here, we report a case of Hashimoto thyroiditis-associated thyroid cancer whose APTT was isolated prolonged and discuss the challenges of diagnosis and clinical management of this patient.Patient concerns:A 57-year-old woman was admitted to the hospital due to thyroid cancer. Anticoagulant assay was performed for this patient before surgery, she had normal values for prothrombin time, thrombin time, and fibrinogen, but had isolated prolonged APTT value (20 seconds longer than normal). However, the routine laboratory of the local hospital showed normal APTT and she did not have any abnormal bleeding or thrombotic episodes. Lupus anticoagulant (LA) was strongly positive according to mixing studies and modified dilute Russell viper venom time method, it was responsible for prolonged APTT.Diagnoses:Hashimoto thyroiditis-associated thyroid cancer whose APTT was isolated prolonged.Interventions:The isolated prolongation of APTT in this patient was due to LA. She had no history of anticoagulant medications and no spontaneous bleeding episodes. There should be no specific intervention before thyroidectomy.Outcomes:This thyroid cancer patient had an uneventful surgery and was discharged after a week.Lessons:Prolonged APTT is not considered an absolute indication for plasma infusion therapy in patients with LA. The correct identification of the cause of APTT prolongation is essential for proper treatment of the individuals.