INR

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Background

  • International Normalized Ratio; standardized measure of the extrinsic coagulation pathway
  • Based on prothrombin time (PT) corrected using an international sensitivity index

Normal Values

  • Normal: 0.8-1.1
  • Therapeutic anticoagulation (warfarin): typically 2.0-3.0 (mechanical valve: 2.5-3.5)

Interpretation

  • Elevated INR: warfarin use, liver disease, DIC, vitamin K deficiency, factor VII deficiency
  • Supratherapeutic INR on warfarin: hold warfarin, vitamin K (PO or IV), consider 4-factor PCC for serious bleeding[1]
  • INR is not validated for assessing coagulation in patients on DOACs
  • INR does not reliably predict bleeding risk in cirrhosis (due to balanced coagulopathy)

See Also

References

  1. ↑ Tomaselli GF, et al. 2020 ACC Expert Consensus Decision Pathway on Management of Bleeding in Patients on Oral Anticoagulants. J Am Coll Cardiol. 2020; 76(5):594-622. PMID 32680646.
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