Gene Symbol: SLC26A4
Chromosomal Locus: 7q31
Protein: Solute Carrier Family 26, member 4
Pseudonyms: DFNB4, NS-EVA, PDS, Pendrin
TURNAROUND TIME: 4 weeks
TESTING METHODOLOGY: Polymerase chain reaction (PCR) and DNA Sequencing of all 21 exons, and their intron-exon borders.
- Collect: Prefer two 5ml whole blood EDTA (lavender top) tube.
- Min. Collection: 0.7 ml whole blood EDTA.
- Transport: blood EDTA at Room Temp shipped regular next day air (No Saturday delivery; store specimen at 4°C and ship Monday).
- Stability: Ambient: up to 7 days; Refrigerated: 2 weeks. Frozen: unacceptable
- Unacceptable Conditions: Serum. Frozen or severely hemolyzed blood. Clotted blood.
- Prenatal testing: Direct: 5ml direct unspun amniotic fluid or 15mg CVS tissue with a backup flask growing. Culture: confluent T25 flask. Maternal blood sample is required for maternal cell contamination studies.
Counseling and informed consent are recommended for genetic testing. A consent form
is available as a resource but not required.
Incidence: Unknown, however estimated to account for 7.5% of all congenital deafness.
Inheritance: Autosomal recessive.
Disease Characteristics: Sensorineural hearing impairment that is usually congenital, non-progressive, and severe to profound; enlarged vestibular aqueduct [EVA]); abnormal perchlorate discharge test or goiter, generally occurring in late childhood or adolescence. Mondini malformation may also be present. Isolated enlarged vestibular aqueduct [EVA]-related hearing loss may occur with a single mutation.
Molecular Genetic Mechanism: A variety of missense, nonsense and insertion/deletion mutations have been described in the gene.
Clinical Sensitivity: 50%- 90%
Analytic Sensitivity: >99%
Test Limitations: Mutations located outside the tested region will not be detected. Rare diagnostic errors can occur due to primer or probe site mutations or rare polymorphisms.
INDICATIONS FOR USE:
- To determine whether a hearing defect in a child is hereditary.
- To identify the potential for abnormal thyroid function and risk of goiter.
- To assess the risk of having a child with hearing loss.