Anticoagulation Monitoring

The following recommendations are to assist clinicians in selecting which laboratory tests to use for monitoring heparin, low molecular weight heparin, direct thrombin inhibitors and/or oral anticoagulant therapy as well as the therapeutic/reference range when available. This guideline is mandated by the College of American Pathologists, (HEM.23575).

 
Guidelines for Anticoagulation Monitoring: Testing Available at ITxM Diagnostics
ANTICOAGULANT ITxM DIAGNOSTICS TEST NAME AND ORDER CODE THERAPEUTIC / REFERENCE RANGE (est. by ITxM Diagnostics)
Warfarin (Coumadin®) PT/INR

Chromogenic Factor X (537I)*
INR: 2.0 - 4.0 (Therapeutic)

Range corresponding to INR: 47%-23% (lower value correlates to higher INR)
Unfractionated Heparin (UFH) Heparin Level/Anti-Xa Level (547L)

Please indicate unfractionated heparin when ordering
0.3 - 0.7IU/mL (Therapeutic range for IV administration)
Low Molecular Weight Heparin (LMWH) Heparin Level/Anti-Xa Level (547L)

Please indicate type of heparin (Lovenox, Fragmin) when ordering.

Check peak anti-Xa level 3-4 hours after a dose.
0.6 - 1.0 IU/mL
Therapeutic range for q12h dose)

1-1.5 IU/mL
(Therapeutic range for 1.5 mg/kg q24h dose)

0.2-0.5 IU/mL (Prophylactic range)
Direct Thrombin Inhibitors (DTI):

Dabigatran
Dabigatran Level (5997)

aPTT (5363) and TT (537E)**
See Comment***
Fondaparinux (Arixtra®) Fondaparinux Level (5762)

Check level approximately 3 hours after a dose.
00.62 - 1.26 mg/L
(Therapeutic range for q24h dose)

0.39 - 0.5 mg/L (Prophylactic range)
Rivaroxaban (Xarelto®) Rivaroxaban Level (6095) See Comment****
 

*Chromogenic factor X can be used to monitor warfarin in patients with antiphospholipid antibody syndrome or other inhibitors that might interfere with INR, or in patients on parenteral direct thrombin inhibitors that might interfere with INR.

**No therapeutic ranges or recommendations available for use of aPTT for monitoring DTI. aPTT may be prolonged with DTI, dose dependent. TT (thrombin time) may be prolonged with DTI, however does not have linear correlation and no therapeutic rage is available. A Normal TT may indicate absence or very low level of DTI.

***Plasma dilute thrombin time is used to extrapolate dabigatran concentration in ng/ml. No “therapeutic range” has been established. In patients receiving dabigatran 150 mg BID, peak values of observed serum concentration range is 64-443 ng/mL and through values range is 31-225 ng/ml

****Modified anti-Factor Xa assay utilizing rivaroxaban calibrators used for measuring plasma concentrations. No “therapeutic range” has been established for rivaroxaban monitoring. Observed peak concentrations in individuals exposed to 10 mg daily dose for VTE prevention were 91-196 ng/ml and trough 1.3-38 ng/ml. Observed peak concentrations after exposure to 20mg daily for VTE treatment were 175-360 ng/ml and trough values were 19-60 ng/ml.