Anti Xa for LMW Heparin

General Information

Lab Name: Anti Xa for LMW Heparin
Lab Code: LMWXA
Epic Name: Anti-Xa For Low Molecular Weight Heparin
Description: Low Molecular Weight Heparin (Enoxaparin): Measure 4 hours after the last dose.

Suggested populations to monitor LMW Heparin: renal insufficiency, pregnancy, newborns, markedly obese or underweight patients (pharmacokinetic differences), patients on prolonged therapeutic doses (malignancy, APA, refractory or failed warfarin) to prevent excessive or insufficient anticoagulation.
Synonyms: Anti 10A, anti factor 10, Anti Factor X, anti Xa, Anti Xa Activity, anti-factor 10, anti-factor X, antiXa, AntiXa, dalteparin, enoxaparin, Enoxaparin, fragmin, HEPACT, Heparin Activity, lovenox, Low Molecular Weight Heparin
Components

Method: This method determines a factor Xa inhibitor level by measuring the inhibition of factor Xa cleavage of a chromogenic substrate. Because no exogenous antithrombin is added in this assay, and because antithrombin plays a significant role in factor Xa inhibition with heparin, low molecular weight heparin, or fondaparinux, patients with lower antithrombin levels (<70%) may demonstrate lower anti-Xa activity.
Reference Range: Units: Anti Xa IU/mL
Ref. Range Notes: For more information, visit UW Medicine Anticoagulation Services

Specimen Type: Blood
Collection: 2.7 mL BLUE TOP (CITRATE) Tube Draw 4 hours after last dose
Handling Instructions: Process samples within one hour of collection. If testing cannot be done within 4 hours of processing, re-spin plasma, remove upper layer of plasma and freeze. Send frozen plasma to UW-MT. This test is viable on samples up to 4 hours after initial centrifugation.

Note: Samples that are drawn through a heparinized line may be contaminated by the heparin in the line. Results of this sample would reflect the anti-Xa activity of the heparin in the patient as well as the heparin in the line and may be erroneously increased. Samples containing platelet clumps or hemolysis due to difficult blood draws may show decreased heparin activity due to in vitro platelet activation. If results are unexpectedly low redraw the sample and repeat the test.
Quantity: Requested: 1.0 mL citrated plasma
Minimum: 0.5 mL citrated plasma

Receiving Instructions: Take whole blood specimen to COAG Lab

HMC SPS: Send samples after processing and freezing with the next courier run. If STAT, send immediately with STAT Delivery Express.

Outside Laboratories: Centrifuge for 10 minutes, remove plasma & re-spin for another 10 minutes. Remove upper layer of plasma and freeze (1 mL) @ -20 ˚C to - 80 ˚C. Send Frozen on dry ice. Process samples within one hour of collection.

Lab Department

Coagulation(COAG)

Frequency

Daily, perform as received

Available STAT?

Yes

Performing Location(s)

UW-MT	Coagulation 206-520-4600 Clinical Lab, Room NW220, University of Washington Medical Center, 1959 NE Pacific street, Seattle, WA 98195