DNA-NON-SYNDROMIC HEARING LOSS(NSHL) CONEXION 26 in Chennai

DNA Non-Syndromic Hearing Loss (NSHL) Connexin 26 Test: Price, Purpose, Range & Reports

Test Overview

The DNA Non-Syndromic Hearing Loss (NSHL) Connexin 26 Test is a highly focused genetic assay used to investigate the most common genetic cause of congenital hearing loss. It specifically analyses the GJB2 gene, which encodes the Connexin 26 protein. Mutations in this gene are responsible for a large percentage of inherited, non-syndromic hearing impairment worldwide.
Non-syndromic means the hearing loss occurs without any other related medical symptoms affecting non-auditory parts of the body. This test is crucial for clarifying the genetic aetiology of hearing loss, which is essential for determining prognosis and providing accurate family counselling. If you are looking for the Connexin 26 Test price or need to schedule this test, you can search for the service through Apollo 24|7 to find accredited lab testing options near you.

What is the Connexin 26 (GJB2) Test?

The Connexin 26 Test is a laboratory procedure that sequences or analyses specific regions of the GJB2 gene (Gap Junction Beta 2) from a patient's DNA.

The GJB2 gene provides instructions for creating the Connexin 26 protein. This protein forms tiny channels, called gap junctions, in the cells of the inner ear (cochlea). These channels are fundamental for recycling potassium ions, a process required to generate and transmit sound signals to the brain. When mutations disrupt the structure or function of Connexin 26, this necessary ion flow is impaired, resulting in sensorineural hearing loss. The degree of hearing loss caused by GJB2 mutations is typically moderate to profound.

What is the Estimated Price for Genetic Testing?

The price for specialised genetic testing, such as the Connexin 26 analysis, is reflective of the specialised equipment and expert interpretation required for high-precision DNA sequencing. The final cost of the test is influenced by several factors:

• Technology Used: Genetic tests rely on complex sequencing technologies (e.g., Sanger sequencing or Next-Generation Sequencing) performed by highly trained molecular geneticists.
• Scope of Analysis: This specific test focuses on the GJB2 gene. Broader hearing loss panels that test multiple genes are generally more expensive.
• Location and Lab Specialisation: Specialised genetics laboratories with clinical accreditations often charge fees reflective of the high quality and complexity of their services.
• Genetic Counselling: Consultation fees with a certified Genetic Counsellor, highly recommended for this test, may be separate from the lab analysis fee.

What is the Purpose of the Connexin 26 Test?

The primary purpose of the Connexin 26 Test is to provide a precise molecular diagnosis for individuals with suspected inherited hearing loss, which significantly impacts clinical management and family planning.

Doctors and genetic counsellors recommend the test for the following key objectives:

• Aetiology Confirmation: To definitively confirm that mutations in the GJB2 gene are the cause of the patient's hearing impairment. Confirming a genetic cause allows physicians to rule out other possible environmental causes, such as congenital viral infections.
• Prognostic Clarity: GJB2-related hearing loss is generally known to be non-progressive, meaning it will not worsen over time, which provides reassurance to families. This specific diagnosis also helps determine candidacy and expected outcomes for interventions like hearing aids or cochlear implants.
• Reproductive Risk Counselling: For the parents of an affected child, this test identifies if they are carriers of the recessive mutation. This is essential for accurately calculating the recurrence risk (typically 25% for subsequent children) and discussing reproductive options.
• Targeted Newborn Screening Follow-up: The test is often used as a direct, cost-effective follow-up tool for infants who failed their initial newborn hearing screens and have no obvious syndromic features.
• Distinguishing Non-Syndromic Status: A positive GJB2 result reinforces the non-syndromic nature of the hearing loss, minimising the need for extensive, often expensive, investigations for other systemic disorders.

Who Should Get a Connexin 26 Test Done?

The Connexin 26 Test is highly targeted due to the prevalence of GJB2 mutations, making it a critical initial step in the diagnostic workup for many forms of congenital hearing loss.

Doctors may recommend this test if a patient falls into one of these groups:

• Newborns and Infants: Those identified through newborn hearing screening (NBHS) who have failed follow-up audiological testing and exhibit bilateral, sensorineural hearing loss of unknown cause.
• Children and Adults with Prelingual Hearing Loss: Individuals with hearing loss that developed before the acquisition of speech, especially if it is non-progressive and bilateral. The severity can range from mild to profound.
• Individuals with a Family History: Patients who have known relatives, particularly siblings, with early-onset, non-syndromic hearing impairment are strong candidates for screening.
• Targeted Carrier Screening: Parents of an affected child should be offered the test to determine their carrier status, which is necessary for accurate genetic counselling regarding future pregnancies.
• Candidates for Cochlear Implantation: Identifying the GJB2 status can sometimes influence the timing or approach to implantation, though it rarely disqualifies a candidate.

Understanding a Connexin 26 Test Report: Inheritance

The hearing loss associated with the GJB2 gene is predominantly inherited in an Autosomal Recessive manner, meaning that an individual must possess two non-functional copies of the gene to exhibit the condition.

• Autosomal Recessive Inheritance
• For a child to have GJB2-related hearing loss:

Both biological parents must be carriers (heterozygous) for a GJB2 mutation, meaning each parent has one normal copy of the gene and one mutated copy.

• The child must inherit the mutated copy from both parents.
• In this scenario, for every pregnancy, there is a 25% chance (1 in 4) that the child will be affected.

Interpreting Specific Results

The report will analyse the two copies of the GJB2 gene (one inherited from each parent). The results are generally categorised as follows: