Connexin-26
The frequency of childhood deafness is estimated to be 1/500.
Half of this hearing loss is genetic and approximately 80% of
genetic hearing loss is nonsyndromic and inherited in an autosomal
recessive manner. Approximately 50% of childhood nonsyndromic
recessive hearing loss is caused by mutations in the connexin
26 (Cx26) gene (GJB2/DFNB1), making it the most common form of
autosomal recessive nonsyndromic hearing loss with a carrier
rate estimated to be as high as 1 in 36 (2.8%).
Genetics analysis fo rthe Cx26 gene at the Greenwood
Genetic Center includes complete sequencing of the entire coding region.
Newborns with confirmed hearing loss should have Cx26 testing.
Cx26 testing will help define a group in which approximately
60% will have profound or severe-profound hearing loss requiring
aggressive language intervention.
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 submitted. Please contact the laboratory for more information.
Transport: Please contact the Molecular Diagnostic Lab Coordinator (1-800-473-9411) for shipping information.
The specimen should be kept at room temperature and delivered
via overnight shipping. FedEx 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 Friday can be safely designated for Monday delivery.
Analysis standards: Analysis will be complete within
2-3 weeks of sample receipt. The lab director assesses the quality
and interpretation of results. Technical staff members 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 with 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 and explanations of testing protocols
will be supplied upon request.
CPT Codes: 83890, 83898 (x2), 83904 (x4), 83912
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