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Test Code RIVAR Rivaroxaban, 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 rivaroxaban anti-Xa level to be falsely elevated.

 

This assay is optimized to measure rivaroxaban 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 rivaroxaban 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, below -40 C degrees.

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

Method Name

Chromogenic Assay

Reporting Name

Rivaroxaban, 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

Rivaroxaban, 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, kidney insufficiency, assessment of compliance, periprocedural measurement of drug concentration, suspected overdose, advanced age, and extremes of body weight).

 

Table. Plasma Concentrations of Rivaroxaban in Patient Populations Studied(1)

Patient population/clinical setting

Rivaroxaban dose

C-min (ng/mL)*
 trough plasma concentration (predose)

C-max (ng/mL)**
peak plasma concentration (postdose)

VTE prevention after total hip replacement surgery

10 mg once daily

9 (1-38)

125 (91-196)

DVT treatment (continued treatment)

20 mg once daily

26 (6-87)

270 (189-419)

Stroke prevention in patients with non-valvular AF (CR-CL ≥50 mL/min)

20 mg once daily

44 (12-137)

249 (184-343)

Stroke prevention in patients with non-valvular AF (CR-CL 30-49 mL/min)

15 mg once daily

57 (18-136)

229 (178-313)

Secondary prevention in patients with acute coronary syndrome

2.5 mg twice daily

17 (6-37)

46 (28-70)

 

Median (5th-95th percentile)

*Defined as samples collected 20-28 hours after dosing

**Defined as samples collected 2-4 hours after dosing

Abbreviations not previously defined:

Atrial fibrillation (AF)

Creatinine clearance (CR-CL)

Deep vein thrombosis (DVT)

Reference Values

An interpretive report will be provided.

Interpretation

The lower limit of detection of this assay is 4 ng/mL.

 

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

Day(s) Performed

Monday through Friday

Report Available

1 to 3 days

Specimen Retention Time

7 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
RIVAR Rivaroxaban, Anti-Xa, P 74871-5

 

Result ID Test Result Name Result LOINC Value
RIVA1 Rivaroxaban, Anti-Xa, P 74871-5
RIVA2 Interpretation 69049-5
RIVA3 Cautions 62364-5