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Test Code PTNT Prothrombin G20210A Mutation, Blood


Ordering Guidance


This assay will only detect the F2 c.*97G>A (rs1799963) variant associated with thrombophilia. To detect other pathogenic alterations in the F2 gene of a patient with a laboratory diagnosis of thrombophilia, order F2NGS / F2 Gene Next Generation Sequencing, Varies.

 

This assay will not detect alterations in individuals with thrombophilia caused by mechanisms other than the F2 c.*97G>A variant. For those situations consider ordering AATHR / Thrombophilia Profile, Plasma and Whole Blood.



Specimen Required


Patient Preparation: A previous bone marrow transplant from an allogenic donor will interfere with testing. Call 800-533-1710 for instructions for testing patients who have received a bone marrow transplant.

Container/Tube:

Preferred: Lavender top (EDTA)

Acceptable: Yellow top (ACD solution B), light-blue top (sodium citrate)

Specimen Volume: 3 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send specimen in original tube. Do not aliquot.


Useful For

Patients with clinically suspected thrombophilia

 

Determination of the duration of anticoagulation therapy of venous thromboembolism patients

 

Screening for women contemplating hormone therapy

Genetics Test Information

This test detects the F2 c.*97G>A variant (legacy G20210A).

Method Name

Direct Variant Analysis

Reporting Name

Prothrombin G20210A Mutation, B

Specimen Type

Whole blood

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole blood Ambient (preferred) 14 days
  Frozen  14 days
  Refrigerated  14 days

Reject Due To

Gross hemolysis OK
Gross lipemia OK
Extracted DNA Reject
 

Clinical Information

The prothrombin (PT) F2 c.*97G>A (legacy G20210A) variant is a common variant within the 3' untranslated region of the prothrombin gene, affecting 1.5% to 3% of white Americans, especially persons of southern European ancestry. The F2 c.*97G>A variant is less common among African Americans (carrier frequency of 0.4%). The F2 c.*97G>A variant is associated with a 3-fold increased risk of venous thromboembolism due to increased plasma prothrombin activity among carriers.

Reference Values

Negative

Interpretation

The results will be reported as:

-Negative for the c.*97G>A variant

-Heterozygous for the c.*97G>A variant

-Homozygous for the c.*97G>A variant

Cautions

This assay will not detect alterations in individuals with thrombophilia caused by mechanisms other than the prothrombin F2 c.*97G>A variant.

 

Rare single nucleotide variants under the primers can cause preferential amplification of one allele. In many cases, there is no indication that this interference has occurred. Consequently, the analysis could be done on data from only one allele, which may cause a false-negative result or an incorrect allele frequency (homozygous instead of heterozygous).

 

Patients receiving allogenic stem cell transplants prior to having blood drawn for DNA based testing may have false-normal or abnormal results depending on the genotype of the stem cell donor.

 

Consultations with the Mayo Clinic Special Coagulation Clinic Thrombophilia Center, and/or Medical Genetics are available and may be especially helpful in complex cases or in situations in which the diagnosis is atypical or uncertain. Genetic counseling is recommended before testing asymptomatic family members.

Method Description

An allelic discrimination assay is set up using TaqMan chemistry. End-products are analyzed using a real-time polymerase chain reaction instrument for genotype detection.(Package insert: TaqMan SNP Genotyping Assays. Applied Biosystems; 2014)

Day(s) Performed

Weekly

Report Available

3 to 5 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

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

CPT Code Information

81240-F2 (prothrombin, coagulation factor II) (eg, hereditary hypercoagulability) gene analysis, 20210G>A variant

LOINC Code Information

Test ID Test Order Name Order LOINC Value
PTNT Prothrombin G20210A Mutation, B 24475-6

 

Result ID Test Result Name Result LOINC Value
21803 Prothrombin G20210A Mutation, B 24475-6
21804 PTNT Interpretation 69049-5
21806 PTNT Reviewed By 18771-6