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| 2. |
- Lindahl, Tomas, et al.
(author)
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Effects of the oral, direct thrombin inhibitor dabigatran on five common coagulation assays
- 2011
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In: Thrombosis and Haemostasis. - : F K Schattauer Verlagsgesellschaft MBH. - 0340-6245 .- 2567-689X. ; 105:2, s. 371-378
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Journal article (peer-reviewed)abstract
- Dabigatran is an oral, reversible thrombin inhibitor that has shown promising results in large clinical trials. Laboratory monitoring is not needed but the effects on common coagulation assays are incompletely known. Dabigatran was added to plasma from healthy subjects in the concentration range 0-1,000 μg/l and analysed using several reagents for activated thromboplastin time (APTT), prothrombin time (PT), fibrinogen, antithrombin, and activated protein C resistance. Typical trough concentrations are about 50 μg/l, peak concentrations 100-300 μg/l. At 100 μg/l all APTT-results were prolonged. The concentration required to double APTT ranged between 227 and 286 μg/l, the responses for all five reagents were similar. PT-reagents were much less affected with almost no samples above INR 1.2 at 100 μg/l. The effect was sample dilution dependent with PT Quick type more sensitive than PT Owren type methods. If a patient on dabigatran has prolonged APTT, >90 seconds, and Quick PT INR>2 or Owren PT INR>1.5 over-dosing or accumulation of dabigatran should be considered. Two of four fibrinogen reagents underestimated the fibrinogen concentration considerably at expected peak concentration. Methods based on inhibition of thrombin over-estimated the antithrombin concentration, but not Xa-based. The APC-resistance methods over-estimated the APC-ratio, which may lead to miss-classification of factor V Leiden patients as being normal. Different coagulation assays, and even different reagents within an assay group, display variable effects at therapeutic concentrations of dabigatran. Some of these assay variations are of clinical importance, thus knowledge is needed for a correct interpretation of results.
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- Strandberg, Karin, et al.
(author)
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Evaluation of a rapid automated assay for analysis of von Willebrand ristocetin cofactor activity.
- 2006
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In: Clinical and Applied Thrombosis/Hemostasis. - : SAGE Publications. - 1938-2723 .- 1076-0296. ; 12:1, s. 61-67
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Journal article (peer-reviewed)abstract
- A commercially available turbidometric assay has been evaluated for the measurement of von Willebrand factor ristocetin cofactor activity (VWF:RCo). The assay is simple, rapid, and can be cost-effectively performed on automated coagulation analyzers. This study’s aim is to illustrate the performance of the automated VWF:RCo assay and its capacity to identify patients with von Willebrand disease (VWD). By direct comparison with a conventional VWF:RCo assay, performed on an aggregometer, the concordance between the two assays was 96%. With minor modifications, the automated assay showed a detection level of 0.03 kIU/L with linearity to 2.00 kIU/L. The imprecision of the automated assay was reduced compared to the conventional assay procedure with CV of 6.8% at the 1.00 kIU/L level and 8.6% at the 0.30 kIU/L level. The automated VWF:RCo assay was also suitable as a screening test to detect VWD in patients investigated for the cause of an increased bleeding tendency. In this situation the automated VWF:RCo assay was tested simultaneously with an automated immunoassay for von Willebrand antigen. Receiver operating curves for the diagnosis of VWD showed a greater area under the curve for the automated VWF:RCo assay compared to the immunoassay, 0.98 vs. 0.94, although the difference did not reach significance. In conclusion, the modified automated VWF:RCo assay shows better precision, lower detection limit, is faster to perform with a lower cost per test compared to the conventional aggregometer based VWF:RCo activity method and is an alternative to an antigen immunoassay as a screening test for VWD.
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- Gøtze, Jens Peter, et al.
(author)
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Ny markør ved trombotisk trombocytopenisk purpura
- 2008
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In: Ugeskrift for Laeger. - 0041-5782. ; 170:33, s. 9-2446
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Research review (peer-reviewed)abstract
- Thrombotic microangiopathy can be caused by several conditions which are difficult to diagnose from the clinical presentation alone. Deficient enzyme activity of a newly-discovered enzyme, ADAMTS-13, can lead to thrombotic thrombocytopenic purpura (TTP). Lack of ADAMTS-13 activity causes increased concentrations of high molecular weight von Willebrand factor forms and increased platelet aggregation. Measurement of ADAMTS-13 activity is useful for the diagnosis of TTP and may also be relevant as a prognostic test for recurrent TTP.
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| 7. |
- Hillarp, Andreas, et al.
(author)
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Unveiling the complex effects of direct oral anticoagulants on dilute Russell's viper venom time assays
- 2020
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In: Journal of Thrombosis and Haemostasis. - : Elsevier BV. - 1538-7933 .- 1538-7836. ; 18:8, s. 1866-1873
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Journal article (peer-reviewed)abstract
- Introduction: Dilute Russell viper venom time (dRVVT) assays can be affected by direct oral anticoagulants (DOACs), which may cause false-positive results. However, there are conflicting results indicating significant differences between different reagents and DOACs. Objectives: To evaluate the effect of DOACs on dRVVT assays. Material and Methods: Samples were prepared by adding DOAC (dabigatran, rivaroxaban, apixaban, or edoxaban) to pooled normal plasma in the concentration range 0 to 800 µg/L. Six integrated dRVVT reagents were used, all composed of a screen assay (low phospholipid content) and a confirm assay (high phospholipid content). The screen/confirm dRVVT results were expressed as normalized ratios. To further evaluate the observed differences between tests and DOACs, addition of synthetic phospholipids was used. Results: The dRVVT ratios increased dose dependently for all DOACs, with four of the six tests and the DOAC rivaroxaban having the greatest effect. With one test, the ratios were almost unaffected with increasing DOAC concentration, whereas another test revealed a negative dose dependency for all DOACs. Variable DOAC effects can be explained by different effects on dRVVT screen and confirm clotting time. Adding synthetic phospholipids to samples containing rivaroxaban resulted in greatly reduced screen clotting times and thereby lower calculated dRVVT ratios. Conclusions: There is a great variability in the dRVVT test result with different DOACs. The dRVVT ratios are unaffected for some reagents and this can be explained by an equal dose-dependent effect on both screen and confirm assays. The phospholipid type and content of the different reagents may contribute to the observed differences.
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- Przybyla, Beata, et al.
(author)
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Coordinated responses of natural anticoagulants to allogeneic stem cell transplantation and acute GVHD – A longitudinal study
- 2017
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In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:12
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Journal article (peer-reviewed)abstract
- Background Allogeneic stem cell transplantation (SCT) enhances coagulation via endothelial perturbation and inflammation. Role of natural anticoagulants in interactions between coagulation and inflammation as well as in acute graft-versus-host disease (GVHD) are not well known. The purpose of this study was to define changes in natural anticoagulants over time in association with GVHD. Patients and methods This prospective study included 30 patients who received grafts from siblings (n = 19) or unrelated donors (n = 11). Eight patients developed GVHD. Standard clinical assays were applied to measure natural anticoagulants, represented by protein C (PC), antithrombin (AT), protein S (PS), complex of activated PC with its inhibitor (APC-PCI) and by markers of endothelial activation: Factor VIII coagulant activity (FVIII:C) and soluble thrombomodulin (s-TM) at 6–8 time points over three months. Results Overall, PC, AT and FVIII:C increased in parallel after engraftment. Significant correlations between PC and FVIII:C (r = 0.64–0.82, p<0.001) and between PC and AT (r = 0.62–0.81, p<0.05) were observed at each time point. Patients with GVHD had 21% lower PC during conditioning therapy and 55% lower APC-PCI early after transplantation, as well as 37% higher values of s-TM after engraftment. The GVHD group had also increases of PC (24%), FVIII: C (28%) and AT (16%) three months after transplantation. Conclusion The coordinated activation of natural anticoagulants in our longitudinal study indicates the sustained ability of adaptation to endothelial and inflammatory activation during allogenic SCT treatment. The suboptimal control of coagulation by natural anticoagulants at early stage of SCT may contribute to onset of GVHD.
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| 10. |
- Strandberg, Karin, et al.
(author)
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Fyra nya instrument för analys av blodgaser testade: Behändiga kassetter skall ge bättre användarvänlighet
- 2000
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In: Läkartidningen. - : Swedish Medical Association. - 0023-7205 .- 1652-7518. ; 97:7, s. 698-701
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Journal article (peer-reviewed)abstract
- An entirely new type of blood gas analyser has made its way into the marketplace, to be used, for example, in emergency rooms, intensive care units, ambulances, and bedside with quarantined patients in infectious diseases units. The instruments reviewed here employ new miniaturised analysis circuitry, integrated into the cassette on which the blood sample is applied. These instruments are designed for use by care-givers without specific laboratory training. Four point-of-care blood gas analysers are tested: OPTI 1 (AVL), I-STAT (HP), IRMA (Infiniti) och ABL 70 (Radiometer).
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