Hearing Loss Panel -- Tier I
Download a Test Requisition Form
You can download the Hearing Loss Test Requisition form (69k) in portable document format (.pdf).
You must have Adobe Acrobat" Reader installed on your computer to read this file. You can download Adobe Acrobat" Reader at Adobe's Web site by selecting the version appropriate for your type of computer.
Genes Tested | About the Disorder | Rationale for Testing | Indications | Specimen l Testing Methodology l Sensitivity l Turnaround Time l Cost l CPT Codes l Shipping l Results l Contact Us
Genes Tested
- GJB2 (connexin 26)
- GJB6 (connexin 30)
- 12SrRNA and tRNAser(UCN) mitochondrial genes
Back to Top
About the Disorder
Hereditary hearing loss affects about 1 in 1500 infants and accounts for more than 50% of the causes of childhood deafness. Mutations in many different genes result in hereditary hearing loss. These genes may be inherited in an autosomal dominant, autosomal recessive, X-linked, or mitochondrial manner.
Back to Top
Rationale for Testing
Identification of the specific cause of a child's hearing loss is an important part of a comprehensive hearing loss evaluation. Identification of a specific genetic mutation provides important information about long-term prognosis and medical management. It also provides very specific information on which to base genetic counseling for parents and other at-risk family members. Finally, identification of a genetic mutation, early in the evaluation process, may eliminate the need for further, more invasive and costly medical procedures and tests.
Tier I testing is indicated for patients with sensorineural hearing loss (SNHL) of unknown etiology who have had no previous molecular genetic studies. Tier I testing identifies the most common genetic causes of childhood SNHL and includes testing for mutations in the GJB2, GJB6 and the mitochondrial 12SrRNA and tRNAser(UCN) genes. Mutations in GJB2, which encodes for the protein, connexin 26, are the most frequent cause of autosomal recessive nonsyndromic hearing loss. Mutations in the GJB2 gene are found in various populations, with a carrier rate of approximately 1-in-30 in the United States Caucasian population, and 1-in-20 in the Ashkenazi Jewish population. Deletions in the GJB6 gene are sometimes identified in association with a heterozygous mutation in GJB2 as the cause for hearing loss. Nonsyndromic hearing loss secondary to mutations in the 12SrRNA and tRNAser(UCN ) genes accounts for about 1% of childhood hearing loss in the United States.
Back to Top
Indication
Patient with hearing loss of unknown etiology and no previous molecular genetic studies.
Note: Children with enlarged vestibular aqueduct(s) may benefit for molecular testing for mutations in the SLC26A4 gene for Pendred syndrome prior to Tier I testing.
Back to Top
Specimen
At least 2 mls whole blood in purple top (EDTA) tube. Alternately, two cytobrushes (cheek swabs) may be collected. (Please call 1-513-636-4474 for a free cytobrush collection kit). Label each tube or brush with patient's name, birth date and date of collection.
Back to Top
Testing Methodology
PCR-based sequencing of exon 2 and the exon1/intron1 boundary of the GJB2 gene; PCR and gel electrophoresis of the 342kb deletion in the GJB6 gene; PCR based sequence analysis for the specific mutations A1555G, C1494T, A7445G, and C7511T in the 12S rRNA and tRNAser(UCN ) mitochondrial genes.
Back to Top
Test Sensitivity and Specificity
Overall, approximately 40% of the genetic causes of hearing loss can be identified through our cost-effective Tier I hearing loss panel. Mutations in the GJB2 gene account for approximately 18% of congenital SNHL in our Midwestern U.S. population. PCR-based sequencing detects > 99% of mutations (nucleotide substitutions, and small base pair insertions and deletions) in GJB2. Deletions in the GJB6 gene are identified in approximately 10% of individuals with hearing loss and heterozygous mutations in GJB2. The 342kb deletion in GJB6 is the most commonly identified deletion in this gene; this test methodology does not detect other very rare deletions in GJB6. Approximately 1% of individuals with hearing loss carry a mutation in one of the mitochondrial genes associated with non-syndromic hearing loss, specifically 12SrRNA and tRNAser(UCN). 70% of the mitochondrial mutations related to non-syndromic hearing loss are detected by our targeted mutation screening protocol.
Back to Top
Turnaround Time
3 weeks
Back to Top
Cost
Please call 866-450-4198 for current pricing, discounts and insurance preauthorization.
Back to Top
CPT Codes
83890, 83898(x5), 83894(x3), 83891(x4), 83904(x10), 83912, 84378
Back to Top
Shipping Instructions
Please enclose test requisition and audiogram with sample. All information must be completed before sample can be processed. Place samples in styrofoam mailer and ship at room temperature by overnight Federal Express to arrive Monday through Friday.
Ship to
Cytogenetics and Molecular Genetics Laboratories
3333 Burnet Avenue NRB 1042
Cincinnati, OH 45229
513-636-4474
Back to Top
Results
Each Tier I hearing loss panel test report includes a detailed interpretation of the genetic findings, the clinical significance of the result, and specific recommendations for clinical management and additional testing, if warranted. Results will be reported to the referring physician or health care provider as specified on the test requisition form.
Back to Top
Contact Us
For additional inquiries, contact us:
Phone 513-636-4474
Fax 513-636-4373
Email moleculargenetics@cchmc.org
Back to Top
