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Test Code APIXA Apixaban, Anti-Xa Assay, Plasma

Important Note

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.

If monitoring levels of Unfractionated Heparin, please order the Unfractionated Heparin Anti-Xa Assay

If monitoring levels of Low Molecular Weight Heparin, please order the Low Molecular Weight Heparin Anti-Xa assay.

Specimen Requirements

Specimen Type:

Whole Blood

Container Type:

Blue top: 2.7 mL or 1.8 mL

Optimal Collection Volume:

  • 2.7 mL in solid blue top tube or 1.8 mL in clear blue top tube.  The correct fill volume is indicated by the etched line on the tube.
  • Click here to view the specimen collection guide for blue top (citrate) tubes.

Collection Instructions:

  1. Do not draw from an arm with a heparin lock.
  2. Gently invert 5 to 10 times to mix blood.
  3. If collected through a blood collection set (butterfly), a discard tube must first be drawn to eliminate dead space from tubing.  

Specimen Transport Temperature:

  • Room temperature for up to 4 hours. If testing is delayed, separate plasma and freeze (see outpatient collection instructions below).
  • Specimens cannot be refrigerated

Processing Instructions:

  1. Centrifuge sample within 4 hours of collection. Platelet-poor plasma must be obtained per laboratory procedure.
  2. If testing will be delayed >4 hours from collection, aliquot plasma into a separate vial and freeze immediately.

Outpatient collections

  1. Spin down the sample, remove plasma, and spin plasma again to obtain platelet-poor plasma.
  2. Separate the platelet-poor plasma into a screw-top vial.
  3. Freeze plasma immediately.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Specimen Stability

Specimen Type

Temperature

Time

Whole blood

Room Temperature

1 hour

Platelet Poor Plasma

Room Temperature

24 hours

Platelet Poor Plasma Refrigerated 2-8 C 7 days

Platelet Poor Plasma

Frozen at - 20 C

24 hours

Specimen Rejection Criteria

  • Tube underfilled
  • Refrigerated specimen
  • Clotted specimen
  • Specimen not processed within four hours of collection

Useful For

The measurement of apixaban levels can be useful information in cases where patients may be at risk for major bleeding, for patients experiencing a bleeding episode, perioperative management, or suspicion of apixaban overdose. This apixaban assay should not be used as a stand-alone test and the results should be used in conjunction with other clinical and laboratory findings.

Peak and Trough Apixaban Levels by Dose and Indication

Indication

Dosage


Apixaban C-min (ng/mL)
Trough Plasma Concentration

Median (5th-95th percentile)
 

Apixaban C-max (ng/mL)
Peak Plasma Concentration

Median (5th-95th percentile)

Prevention of VTE:
Elective Hip 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)

5.0 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)

Methodology

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

24/7

Expected TAT

Same day

Performing Laboratory

Bronson Laboratory, Coagulation - Kalamazoo and Battle Creek

Sample Retention Time

24 hours

CPT Code

80299