Specimen:

Whole Blood

Collection Medium:

Alternate
Collection Media:

Pink top tube (EDTA sprayed)

Minimum:

Adult preferred minimum: 3 mL whole blood in lavendar top (EDTA) tube
Adult absolute minimum: 1 mL whole blood in lavendar top (EDTA) tube
Pediatric absolute minimum: 1 mL whole blood in lavendar top (EDTA)
                            tube

Testing Schedule:

Testing performed Mondays and Thursdays at reference laboratory.

Analytic Time:

One week upon receipt at reference laboratory.

Reference Range:

By report.

Interpretive Data:

Background Information for Warfarin Sensitivity (CYP2C9 & VKORC1) 3 
Mutations

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.

Comments:

Counseling and informed consent are recommended for genetic testing.

Please refer to the Informed Consent for Molecular Genetic Testing

Test
Limitations:

Mutations other than those targeted will not be detected; analytical 
sensitivity may be compromised by rare primer or probe site mutations.

This test is performed pursuant to an agreement with Roche Molecular 
Systems, Inc.

Methodology:

Polymerase chain reaction followed by unlabeled probe and melting curve 
analysis.

CPT Code:

83891 Isolation; 83898(x3) Amplification; 83896(x3) Nucleic acid 
probes; 83912 Interpretation and report. Additional CPT code modifiers 
may be required for procedures performed to test for oncologic or 
inherited disorders.