Portable prothrombin time (PT) monitors offer the potential for both simplifying and improving oral anticoagulation management. It is necessary to evaluate their concordance and correlation with other PT systems. Our objective was to evaluate the concordance and clinical correlation of two portable PT determination systems, ProTime (ITC) and CoaguChek S (Roche Diagnostics). In all, 20 healthy individuals and 60 anticoagulated patients stabilized over 3 months in a therapeutic International Normalized Ratio (INR) range between 2-3.5 were studied. A drop of capillary blood was obtained simultaneously from two different fingers of each patient and applied to the monitor's application zone. The mean INR of the patients' blood samples of the two monitors differed by 0.01 units (2.32+/-0.63 for Pro Time and 2.33+/-0.68 for CoaguChek). The percentage of simple concordance and the kappa index were 88.3 and 75.9%, respectively. The coefficient of correlation was 0.922. The mean difference (bias) between the monitors was 0.01. The portable PT monitors evaluated presented a high percentage of concordance in INR results.

Self-testing of oral anticoagulation is a new possibility related to the development of portable capillary whole blood prothrombin time monitors. The aim of this study was to evaluate one of this monitors, Coaguchek^®, with respect to its comparability with our routine prothrombin time determination system, as well as with the reference manual technique and two thromboplastins of high sensitivity, Manchester Reagent and one manufactured in our center, Thromboplastin Bilbao, in a group of patients on oral anticoagulant treatment. Although a correlation of r = 0.9271 was found between international normalized ratio (INR) values of Coaguchek and our routine method, Neoplastine/STA analyzer, the difference of the INR scatter increased with the magnitude of measurement, being lowest for INR between the portable monitor and Manchester Reagent and Thromboplastin Bilbao, with a similar coefficient of correlation, r = 0.8948 and r = 0.8905, respectively. A test was performed showing a 65.6% agreement with the INR values of the STA analyzer, 66.4% with Manchester Reagent and 73.4% with Thromboplastin Bilbao. On the basis of this correspondence with laboratory prothrombin time results Coaguchek may be considered as a possible option for monitoring anticoagulated patients even though patients should be given instructions and advice as regards the management and interpretation of the results.

The aim of this study was to evaluate the accuracy of the portable coagulometer CoaguChek^® (Roche Diagnostics) as a prothrombin time (PT) monitor, and to correlate capillary blood results with those of three different routine methods used for monitoring oral anticoagulant therapy (OAT): capillary, plasma and whole blood samples. Three hospitals participated in the study with a total of 235 patients on OAT. The international normalized ratio (INR) results obtained with CoaguChek were compared with those obtained using each of the routine methods. The study presents a good correlation between the PT monitor and the three methods studied: r = 0.9745 (hospital A), r = 0.9283 (hospital B), r = 0.9136 (hospital C). A simplified concordance test of the methods results in a nine-field comparison table showing concordances of 87.2, 85.7 and 68.4%, respectively. The absolute difference (mean ± SD) between laboratory A and CoaguChek INRs was 0.0571 ± 0.2042, with values of 0.04286 ± 0.3906 for laboratory B and 0.6986 ± 0.6170 for laboratory C. These results confirm that CoaguChek could be used as a new method for oral anticoagulant monitoring, and is in best agreement with the capillary blood PT system.

Two models of capillary blood prothrombin time (PT) monitoring systems were evaluated for analytical performance and then compared with two routine PT systems using the reference manual technique and a high-sensitivity thromboplastin. Two sets of 60 and 80 plasmas were analyzed from anticoagulated patients stabilized over 3 months in an INR range 2-3.5 for therapy. Capillary PT determination was performed in two portable monitors, CoaguChek S and CoaguChek PT (Roche Diagnostics), and plasma automatic methods were Neoplastine/STA (Diagnostics Stago) and PT-FibrinogenHsPlus/ACL7000 (Instrumental Laboratories). Thromboplastin Bilbao (TBi), an in-house high-sensitivity rabbit thromboplastin (ISI=1.08), recommended as the reference reagent by an External Spanish Oral Anticoagulant Quality Assessment, was used in the PT manual technique. The two monitors' coefficients of correlation with the reference system were 0.74 for CoaguChek S and 0.81 for CoaguChek PT. The automatic routine systems showed a correlation of 0.92 (Neoplastine/STA) and 0.91 (PT-FbHsPlus/ACL7000). Clinical agreement expressed as the percentage of simple correlation ranged between 75.0% (CoaguChek S) and 88.9% (Neoplastine/STA). The systems having the best kappa index with the manual technique were CoaguChek PT (71.9%) and the Neoplastine/STA system (73%). The routine PT management systems exhibited better correlation and percentage of concordance when using the TBi/manual technique than did the portable monitors, which moreover performed unequally in this regard.

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