Interpretation of Point-of-care INR Results in Patients Treated with Dabigatran

American Journal of Medicine, 04/13/2012

International normalized ratio (INR) levels in patients taking dabigatran are substantially higher using a Hemochron Jr. point–of–care device compared with laboratory values. The authors discourage the use of these devices specifically, as well as the use of the INR in general, for measuring the anticoagulant effect of dabigatran.

Methods

  • The authors compared INR levels in whole blood and plasma using a Hemochron Jr. Signature+ point–of–care device (International Technidyne Corporation, Edison, NJ) with routine laboratory monitoring, using blood from healthy volunteers that was spiked with increasing concentrations of dabigatran.

Results

  • Prothrombin time and INR levels were increased about 2– to 4–fold with the point–of–care device compared with laboratory measures across the plasma dabigatran concentration range 50–1400 ng/mL.
  • At plasma concentrations of dabigatran likely to be observed in patients, at a dose of 150 mg twice daily (60–275 ng/mL), whole blood point–of–care INR values increased from 1.7 to 4.0, versus 1.1 to 1.5 measured with the laboratory coagulometer.
  • Similar differences in prothrombin time were observed in plasma samples.

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