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UW Medicine

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Anticoagulation Service Pharmacists

About UW Department of
Pharmacy Services
University of Washington
Medical Center
Anticoagulation Services
Modified: Friday, July 20, 2007

ALTERNATIVE MONITORING OPTIONS FOR ANTITHROMBOTIC AGENTS AT THE UNIVERSITY OF WASHINGTON MEDICAL CENTER
Terms of Use
Welcome
Clinic Information
Referrals

Referral Form (pdf)
Venous Thromboembolism (VTE)
Optimum Therapeutic Ranges &
Duration of Anticoagulation (pdf)
Warfarin Dose Adjustments
Guidelines for Correction
of Warfarin Over-Anticoagulation
Guidelines for Dosing
& Monitoring Enoxaparin
Peri-Procedural Anticoagulation
Neuraxial Anesthesia
in the Anticoagulated Patient
Heparin Protocols for UWMC
Heparin-Induced Thrombocytopenia
Central Venous Catheter Management
Alternative Monitoring Options for
Antithrombotic Agents at the
University of Washington Medical Center >
Patient Education
Links to Other Anticoagulation Sites
References (coming soon)
Contact Us

When to Call Your Anticoagulation Clinic (pdf)

Table of Contents

  1. Heparin Activity (Anti factor Xa level)
  2. Direct Thrombin Inhibitor Assay
  3. Chromogenic factor X

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I. Heparin Activity (Anti factor Xa level) - Used to monitor low molecular weight heparins; or instead of aPTT in patients with antiphospholipid antibodies that might interfere with aPTT, or in patients with presumed heparin resistance as measured by aPTT.

    • For low molecular weight heparins:
      • Peak for twice daily SQ dosing: 0.5 – 1 U/ml (3-4 hours after dose).
      • Peak for once daily SQ dosing: 1 – 1.5 U/ml (3-4 hours after dose)
      • Trough: < 0.5 U/ml

    • For IV unfractionated heparin: 0.3-0.7 U/ml.

Test order code: HEPACT.

Specimen collection: 5ml blue top tube.

II. Direct Thrombin Inhibitor Assay - Used instead of aPTT to assess DTI therapy when patients have antiphospholipid antibodies that might interfere with aPTT results.

    • For argatroban: 60-100 seconds.
    • For bivalirudin: 60-90 seconds.
    • For lepirudin: 90-160 seconds.

Test order code: DTI.

Specimen collection: 3ml or 5ml blue top tube.

III. Chromogenic factor X - Used instead of INR in patients with antiphospholipid antibodies that might interfere with INR, or in patients on concurrent direct thrombin inhibitors that might interfere with INR.

    • For warfarin: 45% - 25% = INR 2 - 4.

Test order code: CHRF10.

Specimen collection: 3ml or 5ml light top tube (citrate).

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