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EDUCATION IN THE MANAGEMENT OF BLEEDING

A practical, evidence-based guide for front-line physicians on how to Treat the Bleed

Which lab tests can be ordered to determine DOAC activity levels?

DOAC Figure Q2

  • Drug-specific serum levels to precisely test for DOAC levels are not commonly available, and thresholds of clinically significant cut-off values have not been validated with prospective trials
  • Clinician understanding of assays available in local healthcare facilities is important to ensure appropriate result interpretation; consider consultation with laboratory pathologist
  • Direct thrombin inhibitors:
    • Prothrombin Time (PT) and International Normalized Ratio (INR) – not useful
    • Activated Partial Thromboplastin Time (aPTT)
      • When prolonged implies drug presence (highly specific)
      • If normal, cannot exclude drug presence
    • Thrombin Time (TT) or Dilute Thrombin Time (dTT; Hemoclot®)
      • When prolonged drug is present, even if a trivial amount
      • If normal, definitively excludes drug presence (highly sensitive)
  • Factor Xa inhibitors:
    • PT/INR
      • Rivaroxaban, edoxaban – When prolonged implies drug presence (specific); if normal, cannot exclude drug presence
      • Apixaban – if normal, cannot exclude drug presence
    • aPTT – not useful
    • Anti-Xa Level*
      • Level for factor Xa inhibition, specific for the anticoagulant used
          • A positive test indicates that even a trivial amount of drug is present
          • A negative test firmly rules out the presence of factor Xa inhibitor (sensitive test)
      • *If drug-specific levels are not available, a negative test using unfractionated heparin or low-molecular weight heparin-calibrated assays rule out drug presence; a positive test indicates that drug is present

Relative effect of DOAC presence in the plasma on commonly available coagulation assays, which yield qualitative results

 

Direct Thrombin Inhibitors

Factor Xa Inhibitors

Assay

Dabigatran

Apixaban

Edoxaban

Rivaroxaban

PT/INR

+/-

+/-

+/-

++

aPTT

++

-

-

-

TT or dTT

+++

-

-

-

Anti-Xa Level

-

+++

+++

+++

+ implies a prolonged/abnormal value; - implies a normal value

References:     

  1. Douxfils J, Ageno W, Samama CM, et al. Laboratory testing in patients treated with direct oral anticoagulants: a practical guide for clinicians. J Thromb Haemost. 2018;16:209-219.
  2. Samuelson BT, Cuker A, Siegal DM, et al. Laboratory assessment of the anticoagulant activity of direct oral anticoagulants: a systematic review. Chest. 2017;151:127-138.
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