INTRODUCTION: The aim of this study was to raise awareness among laboratory staff and physicians that prothrombin timeinternational normalized ratio (PT-INR) tests are not reliable in patients receiving direct oral anticoagulant treatment and, in particular, dabigatran.
METHODS: PT-INR tests were performed on 151 plasma specimens using 3 coagulation analyzers with different methodologies: (i) the Thrombolyzer XRM (Behnk Elektronik GmbH & Co. KG, Norderstedt, Germany), which uses the optomechanical method; (ii) the Diagon CoagXL (Diagon Ltd., Budapest, Hungary), which uses the optical method; and (iii) the reference method for the study, the Stago STA Compact (Diagnostica Stago SAS., Asnières sur Seine Cedex, France), which uses the mechanical method. All of the results were analyzed using the intraclass correlation coefficient (ICC), Passing-Bablok regression analysis, and Bland-Altman analysis to examine the consistency of measurement techniques. Unacceptable results were observed for accuracy and precision when the analysis included 23 patients who were using the new generation oral anticoagulant dabigatran.
RESULTS: The Stago STA Compact-Thrombolyzer PT-INR ICC was higher than that of Stago STA Compact-Diagon CoagXL, with a narrow 95% confidence interval. Passing-Bablok regression analysis of all of the results revealed a significant deviation from linearity (p<0.01), but there was no significant deviation from linearity when the results of the patients using dabigatran were excluded. Once the patients using dabigatran were excluded, the results of the comparison studies reached more acceptable limits.
DISCUSSION AND CONCLUSION: It was determined that the use of a new generation oral anticoagulant (dabigatran) was a source of preanalytical error. It will be of great benefit for clinicians to communicate with laboratory specialists in the follow-up of patients who are other than traditional anticoagulation cases.