Assignment of international normalized ratio to frozen and freeze-dried pooled plasmas.

Objectives Frozen and freeze-dried plasmas may be used for local prothrombin time system calibration, for direct international normalized ratio (INR) determination, and for quality assessment. The purpose of the present study was to evaluate the usefulness of INRs assigned with various types of thromboplastins to frozen and freeze-dried pooled plasmas obtained from patients treated with vitamin K antagonists. Methods INRs were calculated according to the international sensitivity index (ISI) model using various thromboplastins and instruments, i.e. International Standards for thromboplastin as well as six commercial reagents prepared from rabbit and bovine brain, and recombinant human tissue factor. The uncertainty of the INRs was assessed using the standard deviations of clotting times and ISI values. Commutability of the plasmas was assessed according to the approved Clinical and Laboratory Standards Institute (CLSI) Guideline EP30-A. Validation of a set of six frozen plasma pools for direct INR determination was performed according to the Subcommittee on Control of Anticoagulation of the Scientific and Standardization Committee of the International Society on Thrombosis and Haemostasis (SSC/ISTH) guidelines. Results For all frozen and freeze-dried plasmas, the INRs calculated with bovine thromboplastin Thrombotest were lower than the INRs assigned with other thromboplastins. With a few exceptions, the frozen and freeze-dried pooled plasmas were commutable. When the set of six frozen plasma pools was used for local calibration, the analytical bias of the INR was less than ±10% for all commercial reagents except Thrombotest. Conclusions Processing of fresh plasmas to prepare pooled frozen plasmas and freeze-dried plasmas may lead to different INR assignments depending on the thromboplastin used. Despite minor INR differences, a set of six frozen plasma pools could be used for local calibration by direct INR determination.

Calibration of the 7th British Working Standard for factors II, IX and X, concentrate.

Seven laboratories from 5 different countries participated in the calibration of the 7th British Working Standard (BWS) for blood coagulation factors II, IX and X. The candidate, 15/182, was assayed for Factors II and X potencies against the 4th International Standard (IS) for Factors II and X, Concentrate (11/126) and for Factor IX potency against the 5th IS for Factor IX, Concentrate (14/148). Intra-laboratory GCVs for all 3 factors were less than 10%, with the majority less than 5%. Inter-laboratory GCVs were 3.4%, 3.2% and 2.3% for FII, IX and X respectively. All participants agreed with the value assigned and preparation 15/182 was established by NIBSC in October 2017 as the 7th BWS for FII, IX, X Concentrate with potencies of 6.0 IU/ampoule, 6.7 IU/ampoule and 4.9 IU/ampoule for FII, IX and X respectively.

Reference materials (RMs) for analysis of the human factor II (prothrombin) gene G20210A mutation.

The Scientific Committee of Molecular Biology Techniques (C-MBT) in Clinical Chemistry of the IFCC has initiated a joint project in co-operation with the European Commission, Joint Research Centre, Institute of Reference Materials and Measurements to develop and produce plasmid-type reference materials (RMs) for the analysis of the human prothrombin gene G20210A mutation. Although DNA tests have a high impact on clinical decision-making and the number of tests performed in diagnostic laboratories is high, issues of quality and quality assurance exist, and currently only a few RMs for clinical genetic testing are available. A gene fragment chosen was produced that spans all primer annealing sites published to date. Both the wild-type and mutant alleles of this gene fragment were cloned into a pUC18 plasmid and two plasmid RMs were produced. In addition, a mixture of both plasmids was produced to mimic the heterozygous genotype. The present study describes the performance of these reference materials in a commutability study, in which they were tested by nine different methods in 13 expert laboratories. This series of plasmid RMs are, to the best of our knowledge, the first plasmid-type clinical genetic RMs introduced worldwide.

Thrombogenicity of prothrombin complex concentrates.

Thrombogenicity of factor IX complex or prothrombin complex concentrates (PCC) is a well-acknowledged problem. The exact incidence is unknown but has decreased with the improvement of the quality of coagulation factor concentrates and a more judicious use of these products. The clinical spectrum of thrombogenicity ranges from superficial thrombophlebitis, deep-vein thrombosis and pulmonary embolism, and arterial thrombosis to disseminated intravascular coagulation. Several risk factors have been identified: (a) predisposing clinical factors (underlying disease and clinical condition), (b) therapy factors (dosing, concomitant therapy and drug interactions), and (c) quality of the PCC used. It is generally assumed that the risk of thromboembolic adverse effects is greater in patients with acquired disorders of hemostasis than in patients with inherited coagulation factor deficiencies. In hemophilia B, clinical conditions with an increased risk include large muscle hematomas, immobilization, surgery (especially orthopedic surgery), and liver disease. In acquired disorders of hemostasis, a prethrombotic state can be assumed in all patients where an indication for PCC concentrates is considered. Liver disease and/ or antithrombin deficiency are considered as major risk factors. Therapy factors with an increased risk include large, repetitive doses of PCC. It is assumed that heparin and, in the case of antithrombin deficiency, antithrombin substitution decrease the incidence of thromboembolic adverse effects. Heparin neutralisation with protamine and aprotinin therapy may be additional risk factors. The declining incidence and the recent cluster of fatal thromboembolic adverse events in Germany with one brand of PCC is strong evidence for the crucial role of the quality of PCC in the occurrence of thromboembolic adverse effects.

Virus safety of prothrombin complex concentrates and factor IX concentrates.

Substantial progress in virus safety has been achieved during the past 15 years. Therefore only a few virus transmissions with plasma-derived products have been observed since 1985. Specific steps to eliminate, remove, or inactivate viruses were developed. Although virus safety is of decisive importance, chemical or physical treatment during the manufacturing process need not activate labile coagulation factors that cause the risk of thrombogenicity nor need not create neoantigens that mediate the risk of inhibitor formation. Thus, any new virus elimination procedure has to be evaluated and validated for all safety aspects. A comprehensive framework of regulations and efforts has been set up involving plasma donors, donation centres, manufacturers, regulatory authorities, politicians responsible for legislation, physicians, and patients. Blood and plasma donation centres and pharmaceutic industry follow "Good Manufacturing Practice" and are subject to regular audits and official inspections. Every single donation as well as plasma pools are tested for virus markers. The final products need both a marketing authorization and official batch release; in Germany, supervised by the Paul-Ehrlich-Institute. European integration is the purpose of the European Medicines Evaluation Agency. An alert pharmacovigilance system enables scientifically adequate reactions in any case of a safety problem. The ultimate evidence of product safety is provided by clinical surveillance. By participating in clinical studies, patients themselves are able to contribute significantly to the safety of plasma-derived products. The currently achieved high level of safety should encourage us to take further steps to stabilize this success and to look for further progress, wherever possible.

Rational, high quality laboratory monitoring before, during, and after infusion of prothrombin complex concentrates.

Prothrombin complex concentrates (PCCs) have been used for over thirty years to treat or prevent bleeding due to hemophilia B, vitamin K deficiency, warfarin overdose, liver disease, or deficiency of one of the prothrombin complex factors. This article tries to answer the questions of which profile of laboratory assays is required for the establishment of the diagnosis; what are indications of replacement therapy with PCCs; how to monitor the therapeutic effect; and how to monitor a possible prethrombotic state after PCC infusion. After proposing basic, standard, and optimal profiles of hemostaseological assays, the basic principal characteristics of a quality management satisfying the requirements of good laboratory practice are discussed.

[Determination of prothrombin (factory II) in one step using Taipan venom]. / Determinación de protrombina (Factor II) en un paso con el veneno de Taipan

A new one-stage prothrombin assay using Taipan venom is presented here. Taipan venom converts prothrombin to thrombin in the absence of all coagulation factors known up to the date. The prothrombin concentration in normal adults varied from 64.0% to 159.0% with a mean of 100.64% plus or minus 24.83%.