- Patient Preparation
- Lavender (EDTA) or pink (K2EDTA).
- Specimen Preparation
- Transport 3 mL whole blood. (Min: 1 mL)
- Storage/Transport Temperature
- Unacceptable Conditions
- Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable
Characteristics: Warfarin overdosing can result in life-threatening events, e.g., bleeding. This test does not identify patients at risk for warfarin resistance.
Incidence: Up to 1 percent mortality and 15 percent morbidity due to bleeding complications.
Cause: Mutations in the CYP2C9 and VKORC1 genes. The common CYP2C9 gene mutations (*2 and *3) with the VKORC1 gene promoter mutation (c.-1639G>A), are estimated to account for 40-63 percent of the variability in therapeutic warfarin dose.
Mutations Tested:CYP2C9 *2 (c.430C>T), CYP2C9 *3 (c.1075A>C), VKORC1 (c.-1639G>A).
Allele Frequencies:CYP2C9 *2, 0.08-0.13, 0.02-0.06, and less than 0.01; CYP2C9 *3, 0.06-0.10, less than 0.1, and 0.01-0.04; VKORC1 (c.-1639G>A), 0.42, 0.89, and 0.08 in Caucasian, Asian, and African-American populations, respectively. Other populations are less well characterized. The VKORC1 (c.-1639G>A) is in very strong linkage disequilibrium with the VKORC1 (c.173+1000C>T).
Clinical Sensitivity: 90 percent of CYP2C9 and VKORC1 mutations causing warfarin sensitivity in Caucasians are detected. Less characterized in other populations.
Methodology: Polymerase chain reaction, DNA hybridization, and Electrochemical Detection
Analytical Sensitivity and Specificity: 99 percent.
Limitations: Mutations other than those targeted will not be detected; analytical sensitivity may be compromised by rare primer or probe site mutations. Diagnostic errors can occur due to rare sequence variations.
- INR target
- Nicotine use? Y/N
- Amiodarone co-administration? Y/N
- Height in inches
- Weight in pounds
If this patient information is not provided, the Warfarin Sensitivity (CYP2C9 & VKORC1) 3 Mutations (ARUP test code 0051370), which does not have a customized patient report, WILL BE SUBSTITUTED.
|Component Test Code*||Component Chart Name||LOINC|
|0051371||VKORC1 Allele 1|
|0051372||VKORC1 Allele 2|
|2004334||Warfarin Plus - Amiodarone , Y/N|
|2004335||Warfarin Plus - Nicotine Use, Y/N|
|2004337||Warfarin Plus - Height in Inches|
|2004338||Warfarin Plus - INR, Target|
|2004368||Warfarin Plus - Specimen|
|2004369||Warfarin Plus - Weight in Pounds|
|2004370||Warfarin Plus - Interpretation|
|2004371||EER Warfarin Genotyping Plus|
- Warfarin Sensitivity Genotyping