Point-of-care monitoring of vitamin K-antagonists: validation of CoaguChek XS test strips with International Standard thromboplastin.
ABSTRACT Many patients treated with vitamin K-antagonists (VKA) use point-of-care (POC) whole blood coagulometers for self-testing. The majority of patients in the Netherlands use one type of POC coagulometer, that is, the CoaguChek XS. Each new lot of test strips for the CoaguChek XS is validated by a group of collaborating thrombosis centres. We assessed the International Normalised Ratio (INR) differences between each of 51 new lots of test strips and the International Standard for thromboplastin rTF/95 or its successor rTF/09.
Each year, a particular lot of CoaguChek XS test strips was used as reference lot. The reference lot was validated by comparison to the International Standard, yielding a relationship between the reference lot INR and International Standard INR. Successive lots of test strips were compared to the reference lot by three centres using 19-29 capillary blood samples obtained from VKA-treated patients. Each patient provided two blood drops from the same finger prick, one for the reference lot strip and one for the new lot.
The mean INR differences between each lot and the International Standard varied between -8% and +4%. The mean absolute values of the relative differences varied between 2.4% and 8.1%. There were small but clinically unimportant differences in INR between the first and second drop of blood.
Accuracy of CoaguChek XS INR determinations can be assessed by a group of collaborating centres using a limited number of capillary blood samples. As the mean INR differences with the International Standard were smaller than 10%, the lots were approved for use by the Netherlands Thrombosis Services.
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ABSTRACT: Portable point-of-care (POC) instruments for determination of the whole blood prothrombin time (PT) have been available for the last three decades. Recently, two novel POC instruments for PT and International Normalized Ratio (INR) determination in whole blood have been manufactured. The purpose of this study was to compare INR values obtained with the novel instruments (microINR® and ProTime InRhythm™) to the INR determined with the international standard for thromboplastin rTF/09. In 60 patients treated with vitamin K-antagonists, venous whole blood was analysed with four different types of POC instruments including the novel ones. In the same patients, citrated plasma was analysed with the international standard rTF/09 and the manual tilt tube technique for clotting time determination. We assessed the bias of the INR read from the POC instruments relative to the international standard. To study the imprecision of the two novel POC instruments, duplicate INR determinations were performed. The results obtained with the two novel POC instruments were positively correlated with those of the international standard rTF/09. However, there was a significant bias between INR read from the novel instruments and the INR determined with rTF/09 (P<0.001). The mean bias was -13.7% (MicroINR) and -9.3% (InRhythm). The imprecision coefficient of variation in venous blood was 5.0% and 5.1%, respectively. The imprecision of the two novel instruments is acceptable with respect to the average within-subject variation of the INR. The accuracy of the systems is borderline and should be improved by the manufacturers. Copyright © 2014. Published by Elsevier Ltd.Thrombosis Research 03/2015; 135(3). DOI:10.1016/j.thromres.2014.12.022 · 2.43 Impact Factor
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ABSTRACT: New oral anticoagulants (NOAC) are approved for several indications for prophylaxis and treatment of venous thromboembolism and for prevention of embolism in atrial fibrillation at fixed daily doses without need of laboratory guided dose adjustment. Due to their low molecular weight of about 500 to 600 Dalton and their hydrophilicity free anticoagulant is excreted immediately through glomerular filtration into the urine. Impairment of renal function may increase the plasma concentration of the anticoagulants and lowered creatinine clearance is a declared contraindication. In contrast to the initial aim of development the anticoagulant effect is required to be determined in special clinical situations. Several specific and non-specific assays using plasma samples are currently undergoing standardization. As all NOACs are excreted into the urine, specific assays were developed for this matrix to determine them quantitatively of qualitatively. Urine samples can be easily and repetitively obtained avoiding problems and risks associated with blood sampling. The qualitative assay can be performed as a point of care test (POC) also by the patient by judging the different colours for the absence or presence of the drugs with the naked eye. The test is rapid (results available within 15 min), sensitive, specific and accurate and does not require a purified NOAC as control. The tests may be a tool for clinicians who need to know for treatment decisions if a NOAC is on board or not. As the tests are specific for oral direct thrombin inhibitors and for oral direct factor Xa inhibitors, the indication does not interfere with other qualitative POC test in development using clotting systems. The test may be indicated for patients at acute hospitalization, before surgery or central nervous system puncture anaesthesia, if fibrinolytic therapy is indicated, acute deterioration of renal function, and for control of adherence to therapy.Thrombosis Journal 08/2013; 11(1):15. DOI:10.1186/1477-9560-11-15 · 1.31 Impact Factor
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ABSTRACT: Introduction Point of care devices (POCT) are used for coagulation evaluation in adults. Reduced blood volumes and the direct use of whole blood allow studies when venous puncture is difficult, such as in newborns. Elimination of sample transport is attractive for use in emergencies and intensive care. Objective To prospectively compare neonatal coagulation parameters measured by the GEM®PCL POCT versus a central laboratory. Materials and Methods Prothrombin Time (PT) and activated Partial Thromboplastin Time (aPTT) were performed on whole cord blood (POCT) and plasma (central laboratory) collected from consecutive newborns at Geneva University Hospital. Agreement was assessed with a Bland & Altman plot and intra-class correlation coefficient (ICC) in 213 newborns cord blood; intra-assay variability (repeatability) was assessed using ICC and coefficient of variation (CV). Results 189 samples were available for the agreement analysis, 24 were excluded for technical problems. The 95% limits of agreements in the Bland & Altman plot ranged from -5.6 to 11.6 and from -39.6 to 11.6 seconds for the PT and aPTT, respectively. The ICC between the two methods was 0.28 (CI 95% 0.06 to 0.47) for PT and 0.20 (CI 95% -0.06 to 0.42) for aPTT. Repeatability (ICC) on the 43 eligible samples was 0.46 (CI 95% 0.19 to 0.67) for PT and 0.52 (CI 95% 0.26 to 0.71) for aPTT. The CV was 10.6% and 12% for PT and aPTT, respectively. Conclusions In newborn cord blood, PT and aPTT measurements with the GEM®PCL POCT had poor agreement with the central laboratory and poor repeatability.Thrombosis Research 08/2014; 134(2). DOI:10.1016/j.thromres.2014.05.024 · 2.43 Impact Factor