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Molecular genetic testing, specifically for the GJB6 gene, is conducted to identify mutations that lead to nonsyndromic hearing loss. The GJB6 gene encodes for gap junction proteins, also known as connexin proteins, which are essential for the transport of nutrients, ions, and signaling molecules between adjacent cells. Connexin 30, the protein produced by the GJB6 gene, is particularly important in the functioning of cells located in the brain, skin, and inner ear, specifically within the cochlea. This gene is situated on chromosome 13 and plays a critical role in auditory function. Nonsyndromic deafness, referred to as NFNB1, is an autosomal recessive condition, meaning that an individual must inherit two mutated copies of the gene to exhibit the hearing loss associated with this disorder. Carriers, who possess only one mutated gene, typically do not show symptoms. In certain instances of NFNB1, both copies of the GJB6 gene may experience a deletion of a protein, indicating a monogenic inheritance pattern. Alternatively, a digenic inheritance pattern may occur, where one copy of the GJB6 gene is deleted while a different mutation exists on the neighboring GJB2 gene, leading to impaired function of the gap junctions, reduced potassium levels, and subsequent hearing loss. These genetic mutations disrupt the process of converting sound waves into nerve impulses, which is essential for hearing. Additionally, a less common form of nonsyndromic deafness, known as DFNA3, is characterized as an autosomal dominant disorder, requiring only one altered copy of the GJB6 gene. In this case, a specific amino acid change occurs, where threonine is replaced by methionine at position 5 (Thr5Met), which negatively impacts the activity of the gap junction and affects potassium levels within the cells.
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The GJB6 gene analysis is indicated for individuals who are suspected of having nonsyndromic hearing loss. This includes patients presenting with unexplained hearing impairment that is not associated with other syndromic features. The testing is particularly relevant for those with a family history of hearing loss, as it can help identify genetic factors contributing to the condition.
The procedure for GJB6 gene analysis involves several key steps to ensure accurate identification of genetic mutations. Initially, a sample is collected from the patient, typically through a blood draw or saliva sample, which contains the DNA necessary for analysis. Following sample collection, the DNA is extracted and purified to prepare it for testing. The next step involves the amplification of specific regions of the GJB6 gene using polymerase chain reaction (PCR) techniques. This amplification allows for the detection of common variants associated with nonsyndromic hearing loss, such as the deletions at 309kb and 232kb. Once the target regions are amplified, sequencing or other molecular techniques are employed to analyze the genetic material for mutations. The results of the analysis are then interpreted by a qualified geneticist or molecular biologist, who will provide a report detailing any identified mutations and their potential implications for the patient’s hearing loss.
After the GJB6 gene analysis is completed, patients may receive genetic counseling to discuss the results and their implications for hearing loss. This counseling can help patients and their families understand the genetic basis of the condition, potential risks for other family members, and options for management or intervention. It is also important for patients to follow up with their healthcare provider to discuss any further testing or treatment options that may be indicated based on the results of the genetic analysis. Additionally, patients should be informed about the possibility of carrier status and the implications it may have for future family planning.
| Short Descr | GJB6 GENE COM VARIANTS | Medium Descr | GJB6 GENE ANALYSIS COMMON VARIANTS | Long Descr | GJB6 (gap junction protein, beta 6, 30kDa, connexin 30) (eg, nonsyndromic hearing loss) gene analysis, common variants (eg, 309kb [del(GJB6-D13S1830)] and 232kb [del(GJB6-D13S1854)]) | Status Code | Statutory Exclusion (from MPFS, may be paid under other methodologies) | Global Days | XXX - Global Concept Does Not Apply | PC/TC Indicator (26, TC) | 9 - Not Applicable | Multiple Procedures (51) | 9 - Concept does not apply. | Bilateral Surgery (50) | 9 - Concept does not apply. | Physician Supervisions | 09 - Concept does not apply. | Assistant Surgeon (80, 82) | 9 - Concept does not apply. | Co-Surgeons (62) | 9 - Concept does not apply. | Team Surgery (66) | 9 - Concept does not apply. | Diagnostic Imaging Family | 99 - Concept Does Not Apply | CLIA Waived (QW) | No | APC Status Indicator | Service Paid under Fee Schedule or Payment System other than OPPS | Type of Service (TOS) | 5 - Diagnostic Laboratory | Berenson-Eggers TOS (BETOS) | T1H - Lab tests - other (non-Medicare fee schedule) | MUE | 1 | CCS Clinical Classification | 234 - Pathology |
| XU | Unusual non-overlapping service, the use of a service that is distinct because it does not overlap usual components of the main service | 90 | Reference (outside) laboratory: when laboratory procedures are performed by a party other than the treating or reporting physician or other qualified health care professional, the procedure may be identified by adding modifier 90 to the usual procedure number. | 59 | Distinct procedural service: under certain circumstances, it may be necessary to indicate that a procedure or service was distinct or independent from other non-e/m services performed on the same day. modifier 59 is used to identify procedures/services, other than e/m services, that are not normally reported together, but are appropriate under the circumstances. documentation must support a different session, different procedure or surgery, different site or organ system, separate incision/excision, separate lesion, or separate injury (or area of injury in extensive injuries) not ordinarily encountered or performed on the same day by the same individual. however, when another already established modifier is appropriate it should be used rather than modifier 59. only if no more descriptive modifier is available, and the use of modifier 59 best explains the circumstances, should modifier 59 be used. note: modifier 59 should not be appended to an e/m service. to report a separate and distinct e/m service with a non-e/m service performed on the same date, see modifier 25. | GA | Waiver of liability statement issued as required by payer policy, individual case | GW | Service not related to the hospice patient's terminal condition | XS | Separate structure, a service that is distinct because it was performed on a separate organ/structure |
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| 2013-01-01 | Added | Added |
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