Thrombosis
Panel
Recent research has discovered two mutations within genes
in the blood coagulation pathway that have been implicated as
significant factors for thrombotic risk. These two defects, factor
V Leiden and prothrombin 20210A, are responsible for over 60%
of all cases of inherited thrombophilia. In addition to being
significant risk factors for hypercoagulation, the mutations
are frequently found in, but are not limited to, people of European
descent. Population studies indicate that 2-7% of the Caucasian
population carries the Leiden mutation and up to 3% carry the
prothrombin mutation. Carriers of the Leiden R506Q mutation have
an 8 fold increased risk for venous thrombosis and homozygotes
have a 91 fold increased risk. Specific acquired or environmental
factors may dramatically increase this baseline risk. Mutations
in a third gene, MTHFR, or methylenetetrahydrofolate reductase,
can also increase the risk of thrombosis and other vascular diseases
as a result of elevated serum homocysteine.
Two mutations of
the MTHFR gene, designated "677C-T" and "1298A-C"
are examined. About 35% of the population is heterozygous (carriers)
for the 677C-T mutation. About 33% of the population carries
the 1298A-C mutation. Although the 1298 mutation alone does not
cause elevated homocysteine levels, it can when it coexists with
the 677 mutation. If an individual has two copies of the 677
mutation (homozygote)[12% of the population], or has one copy
of 677 and one copy of 1298 (compound heterozygote)[20% of the
population], he/she will have significantly higher mean plasma
homocysteine concentrations, and the associated higher risk of
vascular disease. The molecular diagnosis of these mutations
is done with the polymerase chain reaction and restriction endonuclease
digestion or allele specific oligonucleotide amplification.
Specimen requirements: 5 to
10 ml of peripheral blood collected
in an EDTA (lavender top) Vacutainer tube is preferred. The
minimal blood needed for reliable DNA isolation is 3 ml. If necessary,
ACD solution A Vacutainer tubes (yellow top) may be substituted.
Buccal swabs for DNA isolation may be accepted in some cases.
Please contact the laboratory for more information regarding
this service.
Transport: Please contact JoAnne Babb (1-800-473-9411),
the Molecular Diagnostic Laboratory coordinator, for shipping
information. The specimen should be kept at room temperature
and delivered via overnight shipping. FedEx delivery is preferred.
If shipment is delayed by one or two days, the specimen should
be refrigerated and shipped at room temperature. Do not freeze
the specimen. Samples collected on a Friday can be safely designated
for Monday delivery.
Analysis standards: Analysis will be completed within
1 week from sample receipt. The quality and interpretation of
test results are assessed by the laboratory director. Technical
staff independently assess the quality and interpretation of
the test. The Greenwood Genetic Center Molecular Diagnostic Laboratory
is CLIA certified and actively participates in CAP proficiency
surveys.
Reporting of Test Results: Test results and their interpretation
will be mailed and/or faxed following completion of the test.
Verbal reports will be telephoned to the person(s) requesting
the test when an abnormal test result occurs. Consultation with
the laboratory director is available and explanations of testing
protocols will be supplied upon request.
CPT Codes:
- panel: 83890, 83894 (x2), 83898, 83912
- Factor V Leiden
alone: 83898, 83912
- Prothrombin 20210A alone: 83898, 83912
- MTHFR C677T and A1298C alone: 83898, 83912
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