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Test Code APIXA Apixaban, Anti-Xa, Plasma


Ordering Guidance


This assay is not indicated for monitoring low-molecular-weight heparin (LMWH) or unfractionated heparin (UFH) concentrations. The presence of UFH and LMWH will cause the apixaban anti-Xa level to be falsely elevated.

 

This assay is optimized to measure apixaban concentration in presence of coagulation factor Xa recombinant, inactivated-zhzo (andexanet alfa, Andexxa).



Necessary Information


 



Specimen Required


Specimen Type: Platelet-poor plasma

Collection Container/Tube: Light-blue top (3.2% sodium citrate)

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions:

1. Specimen should be collected 2 to 4 hours (peak) after a dose or just prior (trough) to the next dose for apixaban concentrations.

2. For complete instructions, see Coagulation Guidelines for Specimen Handling and Processing.

3. Centrifuge, transfer all plasma into a plastic vial, and centrifuge plasma again.

4. Aliquot plasma into a plastic vial leaving 0.25 mL in the bottom of centrifuged vial.

5. Freeze plasma immediately (no longer than 4 hours after collection) at -20° C or, ideally, ≤-40° C.

Additional Information:

1. A double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.

2. Each coagulation assay requested should have its own vial.


Useful For

Measuring apixaban concentration in selected clinical situations (eg, renal insufficiency, assessment of compliance, periprocedural measurement of drug concentration, suspected overdose, advanced age, and extremes of body weight)

Method Name

Chromogenic Assay

Reporting Name

Apixaban, Anti-Xa, P

Specimen Type

Plasma Na Cit

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Plasma Na Cit Frozen 42 days

Reject Due To

  All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Clinical Information

Apixaban, an oral anticoagulant that directly inhibits factor Xa, has been approved by the US Food and Drug Administration for prophylaxis of thrombosis in atrial fibrillation and surgical patients and treatment of venous thromboembolism (VTE). Unlike warfarin, it does not require routine therapeutic monitoring. However, in selected clinical situations, measurement of drug level would be useful (eg, renal insufficiency, assessment of compliance, periprocedural measurement of drug concentration, suspected overdose, advanced age, and extremes of body weight).

 

Table. Predicted Apixaban Steady-State Exposure Concentrations(1)

Dosage

Apixaban

C-min (ng/mL)

trough plasma concentration (predose)

Apixaban C-max (ng/mL)

peak plasma concentration
(2-4 hours postdose)

Prevention of VTE: elective hip or knee replacement surgery

 

 

2.5 mg twice daily

51 (23-109)

77 (41-146)

Prevention of stroke and systemic embolism: NVAF

 

 

2.5 mg twice daily

79 (34-162)

123 (69-221)

5 mg twice daily

103 (41-230)

171 (91-321)

Treatment of DVT, treatment of PE and prevention of recurrent DVT and PE (VTE)

 

 

2.5 mg twice daily

32 (11-90)

67 (30-153)

5 mg twice daily

63 (22-177)

132 (59-302)

10 mg twice daily

120 (41-335)

251 (111-572)

 

Median (5th-95th percentile)

Abbreviations not previously defined:

Nonvalvular atrial fibrillation (NVAF)

Deep vein thrombosis (DVT)

Pulmonary embolism (PE)

Reference Values

An interpretive report will be provided.

Interpretation

The lower limit of detection of this assay is 10 ng/mL.

 

Therapeutic reference ranges have not been established. See Clinical Information for peak and trough drug concentrations observed from clinical trials.

Cautions

Routine monitoring of apixaban is not indicated. Therapeutic reference ranges have not been established, however, peak and trough levels observed in clinical trials at different dosing are available. Apixaban concentration may be affected by drug interactions and liver or renal disease.

Method Description

The apixaban, anti-Xa assay is performed on the Instrumentation Laboratory ACL TOP Family using the HemosIL Liquid Anti-Xa kit. The liquid Anti-Xa kit is a 1-stage chromogenic assay based on a synthetic chromogenic substrate and on factor Xa inactivation. Factor Xa is neutralized directly by apixaban. Residual factor Xa is quantified with a synthetic chromogenic substrate. The paranitroaniline released is monitored kinetically at 405 nm and is inversely proportional to the apixaban in the sample.(Package insert: HemosiL Liquid Anti-Xa kit. Instrumentation Laboratory Company; Rev. 06/2017)

Day(s) Performed

Monday through Friday

Report Available

1 to 3 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

80299

LOINC Code Information

Test ID Test Order Name Order LOINC Value
APIXA Apixaban, Anti-Xa, P 74214-8

 

Result ID Test Result Name Result LOINC Value
APIX1 Apixaban, Anti-Xa, P 74214-8
APIX2 Interpretation 69049-5
APIX3 Cautions 62364-5