Variability in the results of inr (international normalized ratio): a comparison of six commercial thromboplastin brands

Abstract

Introduction: The efficacy and safety in treatment with oral anticoagulants are dependent on the monitoring of the effect of anticoagulants by the prothrombin time (PT). The system INR (International Normalized Ratio) was developed to minimize the variability in the PT, mainly because of the thromboplastin reagent used.
Objective: Compare the results of INR employing six thromboplastins and plasmas of patients using oral anticoagulants.
Materials and Methods: For this study, 96 patients using oral anticoagulants and that had TP collected for monitoring anticoagulants were selected randomly. INR values were determined using six commercially available thromboplastin brands.
Results and Discussion: Of the 96 patients, 29 were with the INR between 2 and 3 when used reagents Dade-Behring®, Human do Brasil® and Diagnostica Stago®. Regardless of the range of INR, the results obtained with the reagent Labtest® were statistically different from the Dade-Behring®, from Diagnostica Stago®, Trinity Biotech and Bios Diagnostica®. With INR between 2 and 3 only differences were observed between the results of brands and Bios Diagnostica® Labtest®. With INR above 3, the results of Labtest® were different from the Dade-Behring®, from Diagnostica Stago®, Trinity Biotech® and Bios Diagnostica®.
Conclusion: Despite the establishment of INR, there are still significant differences in INR results depending on the thromboplastin brand used, which can interfere with the therapeutic approach in relation to oral anticoagulants.