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Test Code LABWARF Warfarin, Serum

Additional Codes

 

Test Name in EPIC EPIC Test Code Mnemonic Mayo Test ID
WARFARIN, SERUM LABWARF WARF WRF

 

Reporting Name

Warfarin, S

Useful For

Monitoring patients whose prothrombin time is inconsistent with the prescribed warfarin dose, particularly when failure to comply or surreptitious drug use is suspected.

Note: This test is not useful for evaluation of the patient with prolonged bleeding time suspected of exposure to rat poisons.

Method Name

High-Performance Liquid Chromatography (HPLC)

Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type

Serum Red


Specimen Required


Container/Tube: Red top

Specimen Volume: 3 mL

Collection Instructions: Spin down within 2 hours of draw.


Specimen Minimum Volume

1.1 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Red Refrigerated (preferred) 21 days
  Ambient  28 days
  Frozen  28 days

Reject Due To

Hemolysis

Mild OK; Gross OK

Lipemia

Mild reject; Gross reject

Icterus

Mild OK; Gross OK

Other

Serum gel tube

 

Reference Values

Therapeutic concentration: 2.0-5.0 mcg/mL

Toxic concentration: ≥10.0 mcg/mL

Day(s) and Time(s) Performed

Tuesday; 11 a.m.

CPT Code Information

80299

LOINC Code Information

Test ID Test Order Name Order LOINC Value
WRF Warfarin, S 4098-0

 

Result ID Test Result Name Result LOINC Value
8760 Warfarin, S 4098-0

Analytic Time

2 days

Cautions

This test is not useful for evaluation of the patient with prolonged bleeding who are suspected of exposure to rat poisons.

 

Patients transfused with fresh-frozen plasma may have a disparity between their warfarin level (elevated) and a relatively normal prothrombin.

Method Description

Serum is extracted with petroleum ether. The extract is chromatographed and the distinctive peaks of the coumarins are identified and quantitated in the ultraviolet spectrum.(O'Reilly RA, Aggeler PM, Hoag MS, Leong L: Studies on the coumarin anticoagulant drugs: the assay of warfarin and its biologic application. Thromb Diath Haemorrh 1962;8:82-95; Fishwick FB, Taylor A: The determination of warfarin in animal relicta. Analyst 1967;92:192-195)

Interpretation

Therapeutic concentration: 2.0 to 5.0 mcg/mL

 

Toxic concentration: ≥10.0 mcg/mL

Specimen Retention Time

14 days

Clinical Information

Warfarin (Coumadin) is an anticoagulant that acts by antagonizing the action of vitamin K resulting in the same coagulation abnormalities produced by vitamin K deficiency.

 

Warfarin reduces the levels of prothrombin and factors VII, IX, and X, thereby prolonging the prothrombin and partial thromboplastin times.

 

Warfarin produces its anticoagulant effect within 36 to 72 hours of initiating therapy, and the duration of action may persist for 4 to 5 days following withdrawal of drug.

 

Warfarin circulates almost completely bound to albumin (>98%), and its half-life ranges from 20 to 60 hours.

 

Abnormal bleeding is the chief complication of overdose.

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

Forms

If not ordering electronically, complete, print, and send a Cardiovascular Test Request Form (T724) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/cardiovascular-request-form.pdf).