False result warning for INRatio coagulation monitoring system

GPs should not use the Alere INRatio coagulation monitoring system in patients with anaemia or raised fibrinogen levels, the manufacturer has advised, as there is a risk that the INR will be underestimated.

It is recommended that patients using the Alere INRatio system have their INR periodically verified using a laboratory method. | SCIENCE PHOTO LIBRARY
It is recommended that patients using the Alere INRatio system have their INR periodically verified using a laboratory method. | SCIENCE PHOTO LIBRARY

Patients with the following conditions should be switched to a laboratory INR method for monitoring their anticoagulant therapy:

  • anaemia of any type with hematocrit <30% (Alere INRatio PT/INR Test Strips) or <25% (Alere INRatio2 PT/INR Test Strips, Heparin Insensitive)
  • any conditions associated with elevated fibrinogen levels, including:
    • acute inflammatory conditions (eg, acute viral or bacterial infections such as pneumonia or influenza)
    • chronic inflammatory conditions (eg, rheumatoid arthritis, Crohn’s disease, ulcerative colitis, infectious liver diseases or inflammatory kidney diseases)
    • severe infection (eg, sepsis)
    • chronically elevated fibrinogen
    • hospitalised or advanced cancer or end-stage renal disease patients requiring hemodialysis
    • any bleeding or unusual bruising, clinically observed or reported by the patient

Further information
Safety alert - INRatio and INRatio2 

If the INR result generated by the INRatio Monitor system falls within the therapeutic range, but there is reason to believe the INR could be significantly different (eg, symptoms such as bleeding or bruising which suggests the therapeutic INR value may be falsely low), testing by an alternative method should be performed immediately.
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