Recommendations for Monitoring Anticoagulant Therapy

Vitamin K antagonists (e.g. Warfarin) therapy: The prothrombin time (PT/INR 2180056) is recommended. For conventional anticoagulation for most indications, an INR of 2.0 to 3.0 is recommended. For certain other indications, more intensive anticoagulation with an INR of 2.5 to 3.5 is recommended.

Unfractionated heparin therapy: The aPTT test (2180059) is recommended. Please call for the current therapeutic range. Alternatively, the Factor Xa Inhibition assay (Heparin Anti-Xa 2190046) may be used. The unfractionated heparin therapeutic range for the Heparin Anti-Xa assay is 0.3 to 0.7 U/mL.

Low molecular weight heparin therapy: The Heparin Anti-Xa/Factor Xa Inhibition assay (2190046) (specify the low molecular weight heparin being used) may be used if monitoring is needed. The therapeutic range is shown on the report with the result. The aPTT should not be used.

Direct thrombin inhibitors (e.g. Hirudin) therapy: The Aptt (2180059) may be used. The desired therapeutic range for Hirudin is an aPTT 1.5 – 2.5 times the mean of the laboratory normal aPTT (or 1.5 – 2.5 times the patient’s baseline aPTT).

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