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Test Code LAB5416 Anti Factor Xa, Plasma

Important Note

Direct oral anticoagulants which inhibit Factor Xa (rivaroxaban, apixaban, edoxaban) positively interfere with this test (e.g. anti-Xa DOACs prescribed concurrently with LMWH or UFH can produce a falsely elevated LMWH/UFH activities).

Severe antithrombin deficiency (less than 50%) can cause falsely low LMWH/UFH activities.

Performing Laboratory

Barnes-Jewish Hospital Laboratory

Methodology

Chromogenic Assay 

Literature References:

Package insert:  HemosIL Liquid Anti Xa (pn20302600), Instrumentation Laboratory, 02/2016

Specimen Requirements

For non hospital patient, call Barnes-Jewish Hospital Laboratory Customer Service at 314-362-1470 for STAT pick-up.

 

Specimen Type: Blood
Container/Tube: Light-blue top (citrate)
Specimen Volume: Full tube
Specimen Minimum Volume: Full tube
Collection Instructions:

  1. Draw a discard blue top tube prior to drawing a light-blue top (citrated) tube if using a Winged Infusion Set.  Discard tube should be under filled and discarded.
  2. Clotted blood or an insufficient specimen is not acceptable.
  3. Avoid phlebotomy techniques which cause hemolysis and heparin contamination.
  4. Follow nursing policy on volume of blood to discard prior to collecting blood from indwelling heparinized catheters.

Analyte Stability:

Whole blood:  1 hour at 18- 24° C or 2 hours 2-8° C

Platelet-free plasma: 12 hours at  18- 24° C

Platelet-free plasma can be frozen at -20 for transport on dry ice up to 72 hours
or stored 6 months at -70° C.

 

Additional Information: If the patient is a hospital patient and the hematocrit is >55%, call Barnes-Jewish Hematology Laboratory at 314-362-5203 for instructions.

 

 

Day(s) Test Set Up

Monday through Sunday

Turnaround Time:
STAT: 1 hour from receipt in laboratory
Routine: 1 hour from receipt in laboratory

Test Classification and CPT Coding

85520

Reference Values

Enoxaparin therapeutic range (peak):

VTE treatment, Q12hr dosing: 0.60-1.00 IUnits/mL

VTE treatment, Q24hr dosing: 1.00-2.00 IUnits/mL

Q24hr dosing for renal impairment (CrCl <30 mL/min): 0.60-1.00 IUnits/mL

VTE prevention: 0.10-0.40 IUnits/mL

 

Anti-Xa therapeutic ranges apply to blood samples drawn 4 hours after last dose (peak).

Unfractionated heparin (UFH) therapeutic range: 0.30-0.70 IUnits/mL

Direct factor Xa inhibitors (rivaroxaban, apixaban): Results must be interpreted qualitatively. No activity detected suggests little anticoagulant activity.

 

In severe antithrombin deficiency, anti-Xa measurement may be inaccurate.

 

Interpretive guidelines developed in adult populations. Interpretive guidelines for pediatric patients have not been rigorously defined.

Specimen Transport Temperature

Ambient Yes/Refrigerate Yes/Frozen Yes

 

Additional Information

Analyte Stability:

Whole blood:  1 hour at 18- 24° C or 2 hours 2-8° C

Platelet-free plasma: 12 hours at  18- 24° C

Platelet-free plasma can be frozen at -20 for transport on dry ice up to 72 hours
or stored 6 months at -70° C.

Laboratory Processing Instructions:
Test performed in BJH Core Lab.

LOINC Code Information

Name LOINC Code
Anti Factor Xa, Plasma 42679-1