凝血酶原时间ISI/INR系统测定中的一些问题及改进意见

目的 对凝血酶原时间（PT）测定ISI／INR系统出现的一些问题提出相应的改进建议。方法 对上海市12家医院在用的仪器和匹配的胛试剂，对日常使用的正常血浆平均凝血酶原时间（MNPT）作调研实测，将结果进行分析；调查试剂的仪器特定（specific）国际敏感度指数（ISI）值与世界卫生组织（WHO）的手工法ISI定标值之间的差异；用2种已知国际标准化比值（INR）的异常参比血浆代替WHO的ISI系统作质控并行比较。结果 12家中有4家日常使用的平均正常凝血酶原时间（MNPT）明显偏离实测值，分别为0．8、0．9、1．0和1．8S。用WHO CRM149R参比，用手工法标定的凝血活酶和109mmol枸橼酸钠抗凝的不同胛值血标本，在Sysmex1500型、C．2000型仪器上测定试剂的仪器特定ISI，其结果比手工法分别减少4．1％和4．7％，但采用HEPES-枸橼酸钠抗凝剂标本时，2种型号仪器的特定ISI比手工法分别减少16．7％及7．7％。用已知INR异常参比血浆，国产品与进口品对照的结果良好。结论 受调研12家中，有4家血凝分析仪器调研时实测的MNPT明显偏离日常使用值。有几家医院试剂的仪器特定ISI值也存在问题，建议纠正。用已知INR异常参比血浆代替WHO手工法标定凝血活酶ISI法作质控，使用简便，又不需MNPT参数，值得推广。     

不同血凝仪国际敏感指数值的对比

目的评价不同血凝仪对国际敏感指数(ISI)的影响。方法模拟WHO标定凝血质的参比方法,用一种已知ISI的凝血质对两种血凝仪的特异性ISI进行标定,并以INR形式报告凝血酶原时间(PT)结果。结果未经标定前,两种血凝仪测得结果差异有统计学意义(P0.05),标定其系统的ISI值后,再以公式国际标准化比值(INR)=凝血酶原时间比值(PR)×ISI得出其结果,结果无差异。结论不同血凝仪对ISI值有一定影响,而对仪器进行标定可以部分避免这种影响。     

凝血酶原时间-国际标准化比值的建立

目的 探讨在测定凝血酶原时间-国际标准化比值（PT-INR）实验过程中建立区域性国际敏感度指数（Local ISI）的方法.方法 在ACL TOP-700全自动血凝仪上使用ISI Calibrate血浆建立INR标准曲线,进行回归分析,计算Local ISI和区域性平均正常PT（Local MNPT）值,并用INRValidte血浆验证INR值.结果 A、B、C、D ISI Calibrate血浆PT值分别为11.75、30.80、43.55、77.55 s.实验所得INR标准曲线的回归方程为：Y= 1.258 4X＋2.412 7,Local ISI为0.79,Local MNPT为11.16,R2为0.999 5,斜率CV为0.6%.利用Local ISI和Local MNPT测定3种不同水平INRValidte血浆的PT-INR平均值分别为2.16、2.90、4.50.结论 利用Local ISI和Local MNPT值测定INRValidte血浆PT-INR具有可信性,是一种实用、可行的校正手段.     

血浆凝血酶原时间测定中建立仪器区域国际敏感指数的实验探讨

目的探讨临床口服抗凝治疗时血浆凝血酶原时间(PT)监测的标准化,为临床提供比较准确的PT-国际标准化比值(PT-INR)结果.方法使用PT-INR校准血浆建立PT测定试剂在不同仪器上的区域性国际敏感度指数(Local ISI),以此对新鲜血浆进行PT测定.结果未经Local ISI校准的PT试剂测定血浆的PT时,INR结果差异较大(P<0.01).试剂经Local ISI校准后,测定血浆PT时,INR结果良好(P>0.05及Kappa>0.75).结论在PT测定时,只要建立仪器和测定试剂的Local ISI, INR结果就具有较好的一致性.     

凝血酶原时间测定标准化的几点探讨

目的探讨不同试剂、报告方式对凝血酶原时问(PT)测定结果的影响,以及标本自身因素对仪器测定PT的影响.方法采用两种不同国际敏感度指数(ISI)试剂,测定正常、异常两组标本,结果用秒数、凝血酶时间比值(PTR)、国际标准化比率(INR)表达,对检测结果做统计学分析.另用梯度溶血、黄疸、脂血标本观察仪器测定PT的干扰情况.结果两种试剂检测抗凝疗法病人血浆时,秒数和PTR差异显著(P＜0.05),而用INR表达的结果则无显著差异(P＞0.05).中度以上的溶血、黄疸、脂血标本干扰仪器测定.结论监测抗凝药物治疗时,应用INR方式报告PT值,尽量采用ISI接近1.0的试剂,中度以上的溶血、黄疸、脂血标本最好用手工法测定.     

口服抗凝治疗中凝血酶原时间测定标准化意义

目的:比较三种凝血活酶试剂对口服华法令抗凝治疗病人血标本测得的血浆凝血酶原时间(PTs),凝血酶原时间比率(PTR)和国际标准化比率(INR)间相关性及三种试剂的敏感性。方法:采用Quick一期法在凝血仪上测定50例华法令抗凝治疗病人的PT、PTR及INR值。结果:各组间PT和PTR均有显著性差异(均P<0.01),但各组间INR结果没有显著性差异(P>0.05);不同ISI凝血活酶所测定的INR变异系数不同,ISI的值越高,INR的CV值越大。结论:三种试剂均可用于口服抗凝剂治疗的PT监测,但必须用INR报告结果,便于室间质评。应选用JSI值低的组织凝血活酶试剂,以确保PT测定结果的准确性。     

凝血酶原时间测定标准化的几点探讨

目的 探讨不同试剂、报告方式对凝血酶原时间（PT）测定结果的影响。以及标本自身因素对仪器测定PT的影响。方法 采用两种不同国际敏感度指数（ISI）试剂、测定正常、异常两组标本，结果用秒数，凝血酶时间比值（PTR）、国际标准化比率（INR）表达， 对检测结果做统计学分析，另用梯度溶血、黄疸、脂血标本观察仪器测定PT的干扰情况。结果 两种试剂检测抗凝疗法病人血浆时，秒数和PTR差异显著（P＜0．05）,而用INR表达的结果则无显著差异（P＞0．05）。中度以上的溶血、黄疸、脂血标本干扰仪器测定。结论 监测抗凝药物治疗时，应用INR方式报告PT值，尽量采用ISI接近1．0的试剂、中度以上的溶血、黄疸、脂血标本最好用手工法测定。     

血浆凝血酶原时间测定中建立仪器区域国际敏感指数的实验探讨

目的　探讨临床口服抗凝治疗时血浆凝血酶原时间 (PT)监测的标准化 ,为临床提供比较准确的PT 国际标准化比值 (PT INR)结果。方法　使用PT INR校准血浆建立PT测定试剂在不同仪器上的区域性国际敏感度指数 (LocalISI) ,以此对新鲜血浆进行PT测定。结果　未经LocalISI校准的PT试剂测定血浆的PT时 ,INR结果差异较大 (P <0 .0 1)。试剂经LocalISI校准后 ,测定血浆PT时 ,INR结果良好 (P >0 .0 5及Kap pa >0 .75 )。 结论　在PT测定时 ,只要建立仪器和测定试剂的LocalISI ,INR结果就具有较好的一致性。     

以国际标准化比率报告凝血酶原时结果的局限性

凝血酶原时(pothrombin time,PT)实验是临床血液学实验室最重要的实验之一,主要用于临床检测组织途径凝血功能和口服抗凝药病人疗效的监测。PT结果的报告方式有多种,但近年世界各国专家推荐的方式有3种：时间秒,凝血酶原比率(prothrombin ratio,PR)和国际标准化比率(international normalization ratio,INR),时间秒表示PT测定结果比较直观,但影响因素较多,稳定性较差。PR是一种减少个别变异因素对PT结果影响的方法,它以病人的PT结果与正常人平均PT结果的比值来报告病人的PT值。PT值(s)和PR值没有考虑到凝血活酶试剂之间的灵敏度差异,而INR的数学模型包含了凝血活酶试剂的灵敏度——国际敏感指数(international sensitivity index,ISI),因而克服了凝血活酶灵敏度的影响。临床上用INR是为了标化凝血活酶试剂,用统一尺度来表示PT测定结果,以便优化口服抗凝剂病人治疗剂量范围。尽管INR／ISI系统有许多优点,但要让世界各地的医院都接受它作为PT报告形式还是有困难。20世纪90年代初,美国麻州88家急诊医院,只有40家用了INR值来报告PT结果［1］,53个美国实验室中有50%不知道他们所用凝血活酶试剂的ISI值［2］。归结其原因,主要还是因为用INR报告PT结果仍有一些不尽人意的地方,另外影响INR值准确性的因素还不仅仅是PR和ISI值。     

凝血酶原时间国际标准化临床应用

凝血酶原时间(PT)是检测外源性凝血因子,以及临床口服抗凝剂治疗剂量控制的重要手段,也是手术前对外源性凝血因子筛选的常规实验.但由于不同的凝血质对结果影响很大,造成可比性很差,失去科学性.笔者根据WHO参比方法,用已知国际敏感度指数(ISI),通过国际标准化比值(INR)的计算,达到统一标准,具有可比性,应用于临床准确可靠.     

A comparison of INRs after local calibration of thromboplastin international sensitivity indexes.

There are approximately 300 reagent/instrument combinations for performing prothrombin times/international normalized ratios (PT/INR) in the United States. Manufacturers and laboratories continually struggle to ensure that the International Sensitivity Index (ISI) of their thromboplastin is accurate for assaying PT/INR. OBJECTIVE: This study reports the feasibility of a new method to locally calibrate ISI of thromboplastin using the mechanical STA automated coagulation analyzer (Diagnostica-Stago Inc.) and two photo-optic coagulation analyzers, the BCS (Dade-Behring) and CA-540 (Sysmex). DESIGN: Neoplastine CI+ (CI+) (Diagnostica-Stago Inc); Thromboplastin C+ (TC+); Thromborel S (TRS); and Innovin (I) (Dade-Behring) were used in this study. A mean normal PT (MNPT) was determined for each reagent/instrument combination using samples from 25 normal individuals. Manufacturer instrument specific ISI values were not available for the STA with TC+, TRS and I. The CA540 had no ISI value for CI+ and the BCS system had no manufacturer assigned ISI values for TC+ and I; generic photo-optic and mechanical ISI manufacturer values were used for these two systems. Local on-site calibration was performed using frozen plasma calibrators to determine ISI values for each thromboplastin. Post-calibration, 95 patient samples were assayed for each reagent/instrument system combination using the manufacturer ISI and the local calibrated ISI to determine the INR result. PATIENTS: Patients from whom samples were obtained included five with a lupus anticoagulant, 30 on heparin therapy, and 60 on coumadin therapy. RESULTS: Differences between manufacturer versus local calibrated ISI ranged from 0.9% to 18.9% for normal sample INRs and from 0.8% to 16.4% for patient sample INRs. The number (or proportion) of patient specimens with clinically significantly different INR values (>10.0% difference) ranged from zero for several reagent combinations to more than half (or >50.0%) of those tested for several other combinations. CONCLUSION: Our results indicated that by locally calibrating ISI values, each laboratory may eliminate variability and guesswork between different reagent/instrument systems for ISI values when performing PT/INR assays and potentially improve the clinical accuracy of their patients' PT/INR results.     

Coagulometer international sensitivity index (ISI) derivation,a rapid method using the prothrombin time/international normalized ratio (PT/INR) Line: a multicenter study

Summary. Background: The original WHO procedure for prothrombin time (PT) standardization has been almost entirely abandoned because of the universal use of PT coagulometers. These often give different international normalized ratio (INR) results from the manual method, between individual makes of instruments and with instruments from the same manufacture. Method A simple procedure is required to derive local INR with coagulometers. The PT/INR Line method has recently been developed using five European Concerted Action on Anticoagulation (ECAA) certified plasmas to derive local INR. This procedure has been modified to derive a coagulometer PT/INR Line providing International Sensitivity Index (ISI) and mean normal PT (MNPT) for coagulometers and give local INR. Results have been compared with conventional ISI calibrations at the same laboratories. Results: With human thromboplastins, mean ISI by local calibration was 0.93 (range: 0.77–1.16). With the PT/INR Line, mean coagulometer ISI was higher, for example 0.99 (0.84–1.23) but using the PT/INR Line derived MNPT there was no difference in local INR. Between‐centre INR variation of a certified validation plasma was reduced with human and bovine reagents after correction with local ISI calibrations and the PT/INR Line. Conclusion: The PT/INR Line–ISI with its derived MNPT is shown to provide reliable local INR with the 13 different reagent/coagulometer combinations at the 28 centres in this international study.     

Guidelines on preparation, certification, and use of certified plasmas for ISI calibration and INR determination.

Reliable international normalized ratio (INR) determination depends on accurate values for international sensitivity index (ISI) and mean normal prothrombin time (MNPT). Local ISI calibration can be performed to obtain reliable INR. Alternatively, the laboratory may determine INR directly from a line relating local log(prothrombin time [PT]) to log(INR). This can be done by means of lyophilized or frozen plasmas to which certified values of PT or INR have been assigned. Currently there is one procedure for local calibration with certified plasmas which is a modification of the WHO method of ISI determination. In the other procedure, named 'direct' INR determination, certified plasmas are used to calculate a line relating log(PT) to log(INR). The number of certified plasmas for each procedure depends on the method of preparation and type of plasma. Lyophilization of plasma may induce variable effects on the INR, the magnitude of which depends on the type of thromboplastin used. Consequently, the manufacturer or supplier of certified plasmas must assign the values for different (reference) thromboplastins and validate the procedure for reliable ISI calibration or 'direct' INR determination. Certification of plasmas should be performed by at least three laboratories. Multiple values should be assigned if the differences between thromboplastin systems are greater than 10%. Testing of certified plasmas for ISI calibration may be performed in quadruplicate in the same working session. It is recommended to repeat the measurements on three sessions or days to control day-to-day variation. Testing of certified plasmas for 'direct' INR determination should be performed in at least three sessions or days. Correlation lines for ISI calibration and for 'direct' INR determination should be calculated by means of orthogonal regression. Quality assessment of the INR with certified plasmas should be performed regularly and should be repeated whenever there is a change in reagent batch or in instrument. Discrepant results obtained by users of certified plasmas should be reported to manufacturers or suppliers.     

International normalized ratio in the prothrombin test: clinical significance and use

The safety and efficiency of therapy by peroral anticoagulants (PA) depend on a laboratory monitoring based on the prothrombin test (PT). The test is distinguished through its variability conditioned by different means of results' presentation as well as through the sensitivity of thromboplastin and a type of a device used in coagulation detection. WHO recommended, 1983, to standardize the thromboplastin preparations through adjusting their sensitivity (the so-called International Sensitivity Index--ISI) to blood coagulation defects induced by PA versus the primary international reference thromboplastin. Thromboplastin ISI as well as the mean normal prothrombin time (MNPT) of blood plasma are used to calculate the international normalized ratio (INR). The presentation of PT results as INR is justified exclusively for the PA-therapy stabilized patients. The INR system makes it possible to optimize the PA therapy only if the laboratory expert and clinician can clearly understand the PT standardization essence and observe the key WHO recommendations, i.e. definition of a coagulometer-specific ISI by manufacturing companies, estimation of MNPT by laboratories and use of the correct anticoagulant concentration.     

凝血活酶敏感指数对凝血酶原时间测定的影响

本文观察了四种不同国际敏感指数的凝血活酶试剂，在相同条件下，对２５例正常人和５０例口服华法令病人进行了ＰＴ测定，结果显示正常参考值随所用凝血活酶的ＩＳＩ不同而异。建议各实验室应依其所用试剂建立自己实验室的正常参考值。对口服抗凝药的５０例患者测得ＰＴｓ（秒）和ＰＴＲ（比率）经方差分析，四组结果有显著性差异（Ｐ〈０．０１），而按ＩＮＲ＝ＰＴＲ＾ＩＳＩ换算成国际标准化比率（ＩＮＲ）后，经方差分析，四组Ｉ     

Effect of lepirudin on the international normalized ratio

BACKGROUND: Many patients receiving direct thrombin inhibitor (DTI) therapy require transition to warfarin. This transition may be complicated by DTI-induced elevations in the international normalized ratio (INR). While the effect of argatroban on the INR has been characterized, data assessing the effect of lepirudin on the INR are limited. OBJECTIVE: To evaluate the effect of lepirudin on the INR. METHODS: Patients receiving lepirudin therapy between January 2000 and May 2001 were identified using the pharmacy database, and a retrospective chart review was conducted. Patients were included for analysis if they had paired activated partial thromboplastin time (aPTT) and INR data while receiving lepirudin monotherapy. RESULTS: Fifty-three paired aPTT and INR data points from 8 patients receiving lepirudin monotherapy were collected. The Organon MDA 180 instrument was used for aPTT and prothrombin time (PT) determination. Organon MDA Platelin L reagent was used for the aPTT and Organon Simplastin L reagent was used for the PT. The international sensitivity index (ISI) of the Simplastin L thromboplastin was 2.0. The mean +/- SD lepirudin dose was 0.05 +/- 0.04 mg/kg/h. Linear regression was used to identify the INRs that correspond to a therapeutic aPTT value of 45-75 seconds (1.5-2.5 times mean laboratory normal of 30 sec). The correlation between aPTT and INR was 0.77. An aPTT of 45-75 seconds with lepirudin correlated to an INR of 1.6-3.2. CONCLUSIONS: Based on laboratory results, when using a thromboplastin with an ISI of 2, lepirudin appears to elevate the INR in the absence of warfarin.     

The prothrombin time/international normalized ratio (PT/INR) Line: derivation of local INR with commercial thromboplastins and coagulometers – two independent studies

Summary. Background: The WHO scheme for prothrombin time (PT) standardization has been limited in application, because of its difficulties in implementation, particularly the need for mandatory manual PT testing and for local provision of thromboplastin international reference preparations (IRP). Methods: The value of a new simpler procedure to derive international normalized ratio (INR), the PT/INR Line, based on only five European Concerted Action on Anticoagulation (ECAA) calibrant plasmas certified by experienced centres has been assessed in two independent exercises using a range of commercial thromboplastins and coagulometers. INRs were compared with manual certified values with thromboplastin IRP from expert centres and in the second study also with INRs from local ISI calibrations. Results: In the first study with the PT/INR Line, 8.7% deviation from certified INRs was reduced to 1.1% with human reagents, and from 7.0% to 2.6% with rabbit reagents. In the second study, deviation was reduced from 11.2% to 0.4% with human reagents by both local ISI calibration and the PT/INR Line. With rabbit reagents, 10.4% deviation was reduced to 1.1% with both procedures; 4.9% deviation was reduced to 0.5% with bovine/combined reagents with local ISI calibrations and to 2.9% with the PT/INR Line. Mean INR dispersion was reduced with all thromboplastins and automated systems using the PT/INR Line. Conclusions: The procedure using the PT/INR Line provides reliable INR derivation without the need for WHO ISI calibration across the range of locally used commercial thromboplastins and automated PT systems included in two independent international studies.     

Comparison of local International Sensitivity Index calibration and ''Direct INR'' methods in correction of locally reported International Normalized Ratios: an international study

BACKGROUND: It is no longer feasible to check local International Normalized Ratios (INR) by the World Health Organization International Sensitivity Index (ISI) calibrations because the necessary manual prothrombin time technique required has generally been discarded. OBJECTIVES: An international collaborative study at 77 centers has compared local INR correction using the two alternative methods recommended in the Scientific and Standardization Committee of the International Society on Thrombosis and Haemostasis guidelines: local ISI calibration and 'Direct INR'. METHODS: Success of INR correction by local ISI calibration and with Direct INR was assessed with a set of 27 certified lyophilized plasmas (20 from patients on warfarin and seven from normals). RESULTS: At 49 centers using human thromboplastins, 3.0% initial average local INR deviation from certified INR was reduced by local ISI calibration to 0.7%, and at 25 centers using rabbit reagents, from 15.9% to 7.5%. With a minority of commercial thromboplastins, mainly 'combined' rabbit reagents, INR correction was not achieved by local ISI calibration. However, when rabbit combined reagents were excluded the overall mean INR deviation after correction was reduced further to 3.9%. In contrast, with Direct INR, mean deviation using human thromboplastins increased from 3.0% to 6.6%, but there was some reduction with rabbit reagents from 15.9% to 10% (12.3% with combined reagents excluded). CONCLUSIONS: Local ISI calibration gave INR correction for the majority of PT systems but failed at the small number using combined rabbit reagents suggesting a need for a combined reference thromboplastin. Direct INR correction was disappointing but better than local ISI calibration with combined rabbit reagents. Interlaboratory variability was improved by both procedures with human reagents only.     

Clinical utilization of the international normalized ratio (INR)

The prothrombin time (PT) is one of the most important laboratory tests to determine the functionality of the blood coagulation system. It is used in patient care to diagnose diseases of coagulation, assess the risk of bleeding in patients undergoing operative procedures, monitor patients being treated with oral anticoagulant (coumadin) therapy, and evaluate liver function. The PT is performed by measuring the clotting time of platelet-poor plasma after the addition of calcium and thromboplastin, a combination of tissue factor and phospholipid. Intra- and interlaboratory variation in the PT was a significant problem for clinical laboratories in the past, when crude extracts of rabbit brain or human placenta were the only source of thromboplastin. The international normalized ratio (INR), developed by the World Health Organization in the early 1980s, is designed to eliminate problems in oral anticoagulant therapy caused by variability in the sensitivity of different commercial sources and different lots of thromboplastin to blood coagulation factor VII. The INR is used worldwide by most laboratories performing oral anticoagulation monitoring, and is routinely incorporated into dosage planning for patients receiving warfarin. Although the recent availability of sensitive PT reagents prepared from recombinant human tissue factor (rHTF) and synthetic phospholipids eliminated many of the earlier problems associated with the use of crude thromboplastin preparations, local instrument variability in the INR still remains a problem. Presently, the use of plasma calibrants seems the best solution to this problem. Standardizing the point-of-care instruments for INR monitoring is another dilemma faced by the industry. Ultimately, new generations of anticoagulant drugs may eliminate the need for laboratory monitoring of anticoagulant therapy.