Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.6 (thromboplastin)
 13,278 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

One hundred and twenty-nine centres in the U.K. participated in a study to test the reliability of the three methods of correction for coagulometer effects on international normalized ratios (INR). Results from 37 centres which tested three warfarinized plasmas by the manual method were taken as the 'true' INR for the assessment of coagulometers. 63 centres (11 manual and 52 using coagulometers) determined their local International Sensitivity Index (ISI) in a calibration exercise. This was performed with a set of 20 lyophilized plasma calibrants with certified manual prothrombin times for the thromboplastin used in the study. The following methods of INR derivation were compared by assessing the percentage deviation from the three INR values established by 37 manual users: I. No coagulometer correction, i.e. (local PT/reference manual normal PT)manual ISI II. Coagulometer ratio correction, i.e. (local coagulometer PT/local coagulometer MNPT)manual ISI III. Local system ISI, i.e. (local coagulometer PT/local coagulometer MNPT)local system ISI IV. System ISI, i.e. (local coagulometer PT/local coagulometer MNPT)system ISI The local system ISI with the plasma calibrants (method III) gave the most reliable correction (mean deviation from 'true' INR 4.87%). The method which gave the least was with the coagulometer ratio correction, i.e. the manual ISI and local coagulometer MNPT (mean 11.25%). The system ISI tested with ACL coagulometers gave less correction than the local ISI calibration. The local system calibration with lyophilized plasmas also avoids some of the constraints on conventional thromboplastin calibrations.
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PMID:The correction of coagulometer effects on international normalized ratios: a multicentre evaluation. 780 51

Local ISI calibration has been proposed to improve INR accuracy and inter-laboratory precision. We evaluated the affect of local PT calibration on INR precision and accuracy using six levels of frozen plasma calibrants prepared and pooled from normal donors and patients stabilized on sodium warfarin (coumarin) based oral anticoagulant therapy (OAT). Reference prothrombin time (PT) and INR values were assigned to these calibrants in accordance with World Health Organization (WHO) procedure using rTF 95 international reference preparation (IRP) of thromboplastin (human recombinant). These calibrants, along with five similarly characterized individual OAT patient plasmas, were distributed to 127 laboratories in a multi-center study. Calibrant plasmas were evaluated and INR's subsequently determined on the 5 OAT test samples using: 1) the ISI and MNPT in place before the study (the local system), 2) the locally calibrated ISI value (local system with ISI calibration) and 3) a PT-INR calibration curve. Precision of INR results improved across the study group using the local system with ISI calibration and the PT-INR calibration curve methods, while accuracy of INR results improved using the PT-INR calibration curve approach only and not the local ISI calibration. The authors conclude that frozen plasma calibrants can be used locally to enhance precision and accuracy of PT results as reported in INR. These calibrants are effective over a range of reagents and instrument combinations. Furthermore, the PT-INR calibration curve appears to be the superior method for local calibration.
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PMID:Evaluation of frozen plasma calibrants for enhanced standardization of the international normalized ratio (INR): a multi-center study. 1184 60

The European Concerted Action on Anticoagulation has been concerned over its first 4 years with both clinical and laboratory aspects of oral anticoagulation in 16 European states. A number of relevant reports have been published which are summarised. In a clinical study from 5 centres with no previous experience of computer dosage a randomised multicentre investigation of a computer dosage program has demonstrated the significant benefit from a computer dosage program compared to traditional (manual) dosage by experienced medical staff. Not only was there greater success in achieving the target INR intervals, but less dose adjustment with the computerised program. The benefit of computer dosage which is widely available, may be even greater at less specialised centres or where there is less interest in anticoagulant dose administration. Laboratory studies have been principally with the assessment of the value of lyophilized plasmas in local ISI calibration. Lyophilized plasmas have been used because their use avoids the necessity for the discarded manual PT technique and the provision of thromboplastin reference preparations. Both lyophilized artificially depleted and coumarin plasmas were shown to give acceptable ISI in ECAA multicentre studies. They differed from the fresh plasma ISI by a measurable but clinically acceptable amount. The two types of lyophilized plasma differed from each other to a greater degree. A minimum of 20 artificially depleted with 7 normal plasmas was required for reliable calibration with a low ISI reagent. For fresh plasma calibrations the current WHO recommendation of 60 fresh coumarin and 20 normal plasmas is substantiated by the ECAA studies. Lyophilized plasmas should be used only for "like-to-like" calibrations. Lyophilized normal plasmas cannot reliably replace the fresh plasma MNPT as they give prolonged results with low ISI thromboplastins. Where coagulometers disturb ISI, local INR correction with certified artificially depleted plasmas is advantageous and considerably increases inter-laboratory precision. Linear regression analysis in place of orthogonal regression does not appear advisable for local coagulometer ISI calibration.
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PMID:European Concerted Action on Anticoagulation (ECAA): Clinical and Laboratory Studies. 2741 85