International Normalized Ratio and Activated Partial Thromboplastin Time Test

History of bleeding is the strongest predictor of an inherited bleeding disorder

INR and aPTT have low sensitivity (1.0% to 2.1%) for bleeding disorders. 1 Clinicians considering an inherited bleeding disorder should first use a Bleeding Assessment Tool (BAT).2 A negative BAT score has close to 100% sensitivity to rule out von Willebrand disease (the most common inherited bleeding disorder). most common).2 A positive BAT score should prompt referral to a hematologist for review of specialized coagulation tests.1

International normalized ratio and APTT test are not indicated before low-risk surgery or interventional radiology

Abnormal INR or aPTT results are not associated with an increased risk of bleeding in low-risk procedures.3,4 An abnormal result with no history of bleeding or use of anticoagulants should be repeated to rule out artifacts or sample handling errors. Investigation is generally not indicated for an APTT less than 4 seconds above the upper limit of normal.2

An abnormal INR or APTT in a bleeding patient suggests a potential medical emergency

Actionable causes of bleeding, such as use of blood thinners, severe liver disease, or acquired hemophilia, may be indicated by elevated INR or aPTT, respectively.5

Clinical history and drug pharmacokinetics are more important than INR or aPTT results in guiding clinical decision-making in patients taking direct oral anticoagulants (DOACs)

Direct oral anticoagulants variably and inconsistently affect INR and APTT results. If a patient is bleeding, decisions regarding the use of a blood product or reversal medication should be based on the last reported medication dose, renal function, and pharmacokinetics. In some centers, DOAC-calibrated assays are available to assess the presence of clinically relevant drug activity.6

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Sallie R. Loera