Reference Interval:
By report
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| Interpretive Data: |
Background Information for Hearing Loss, Nonsyndromic Panel (GJB2) Sequencing, (GJB6) 2 Deletions and Mitochondrial DNA 2 Mutations:
Characteristics: Nonsyndromic hearing loss (NSHL).
Incidence: Approximately 1 in 2600 for NSHL; 50 percent due to GJB2 mutations, 2-4 percent associated with GJB6 deletions, and 1-2 percent related to
mitochondrial mutations.
Inheritance: Dependent on gene. GJB2: Autosomal recessive; rarely dominant. GJB6: Autosomal recessive; resulting from either two GJB6 deletions or one GJB6 deletion and one GJB2 mutation on the opposite chromosome. Mitochondrial DNA: Dominant maternal inheritance.
Penetrance: Complete for GJB6; variable for GJB2 and mitochondrial DNA.
Cause: Deleterious GJB2, GJB6, and mitochondrial DNA mutations.
Mutations Tested: GJB2: Coding region, intron-exon boundary and 5'-UTR mutations. GJB6: 309kb del(GJB6-D13S1830), previously reported as 342kb, and 232kb del(GJB6-D13S1854). Mitochondrial: m.1555A>G and m.7445A>G.
Clinical Sensitivity: 50-55 percent for Caucasians with NSHL; unknown in other ethnicities.
Methodology for GJB2 Sequencing: Invader assay targets the 35delG mutation in the GJB2 gene; the entire coding region, intron-exon boundaries,
and 5'-UTR of the GJB2 gene is bidirectionally sequenced.
Methodology for GJB6 2 Deletions: Multiplex PCR using deletion-specific primers followed by capillary gel electrophoresis.
Methodology for Mitochondrial DNA 2 Mutations: Targeted bidirectional sequencing of mitochondrial mt-RNR1 m.1555A>G and mt-TS1 m.7445A>G.
Analytical Sensitivity and Specificity: Greater than 99 percent.
Limitations: Rare diagnostic errors can occur due to primer site mutations. GJB2 regulatory region mutations, deep intronic mutations and large deletions or duplications will not be detected. GJB6 and mitochondrial DNA mutations, aside from those targeted will not be detected. The etiology of hearing loss due to other genetic or environmental causes will not be determined.
Counseling and informed consent are recommended for genetic testing. Consent forms are available online at www.aruplab.com.
Refer to Statement C under Testing Information at http://www.aruplab.com.
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| CPT Code(s): |
GJB2: 83891 Isolation; 83898 x2 Amplification; 83904 x3 Sequencing; 83909 Capillary electrophoresis. GJB6: 83900 Amplification; 83901 Muliplex Amplification; 83909 Capillary electrophoresis. mt DNA: 83898 x2 Amplification; 83904 x2 Sequencing; 83909 Capillary electrophoresis; 83912 Interpretation and report - Additional CPT code modifiers may be required for procedures performed to test for oncologic or inherited disorders.
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Cross References: |
Deafness (Hearing Loss, Nonsyndromic Panel (GJB2) Sequencing, (GJB6) 2 Deletions and Mitochondrial DNA 2 Mutations)
, GJB6 (Hearing Loss, Nonsyndromic Panel (GJB2) Sequencing, (GJB6) 2 Deletions and Mitochondrial DNA 2 Mutations)
, Hearing Loss (Hearing Loss, Nonsyndromic Panel (GJB2) Sequencing, (GJB6) 2 Deletions and Mitochondrial DNA 2 Mutations)
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