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Test Code CX 26/30 DNA Connexin 26/30 DNA Analysis

Clinical System Name

Connexin 26/30 DNA Analysis





Connexin 26/30 DNA Analysis: reflexive testing starting with sequence analysis of the Gap Junction Beta-2 Protein GJB2 (connexin 26) gene.  If no variants or two variants are identified by GJB2 sequencing, GJB6 deletion analysis is not performed.  If one heterozygous pathogenic variant is detected by GJB2 sequencing, Gap Junction Beta-6 Protein GJB6 (connexin 30) deletion analysis follows. 


Sample Requirements

Specimen: Whole blood, cord blood

Container(s): Lavender/EDTA

Preferred Vol: 3-10 mL

Minimum Vol: 3 mL


Note: Heparin samples (Green tops) are unacceptable.


Specimen: Extracted DNA

Minimum: 10µg

Note: DNA concentration minimum 50 µg/mL; 260/280 ratio 1.70-2.00


Specimen: Cultured cells

Acceptable:  Fibroblasts

Container(s): T-25 flasks

Preferred Vol: 2 flasks

Processing Instructions

Reject due to: Heparin

Spin: No

Aliquot: No

Temp: Refrigerate

Storage location: Molecular Genetics box in CPA refrigerator #2


Off-site collection: Refrigerate blood samples until ready to ship.  Transport all sample types at room temperature via overnight shipping.


Specimen Type Temperature Time
Cultured cells Room temp 3 days
Whole blood, extracted DNA Room temp 3-5 days
Whole blood, extracted DNA Refrigerated 7 days
Extracted DNA Frozen ok


Note: Whole blood samples > 7days may be submitted to be assessed by our lab for acceptability for testing.


STAT Performed TAT
Contact lab Monday - Friday 2-3 weeks


Performing Laboratory

Seattle Children's Laboratory


Department:  Molecular Genetics Laboratory

Phone: 206-987-3872


Lab Client Services: 206-987-2617


Lab Genetic Counselor:

Reference Range

Interpretive report will be provided


GJB2 (connexin 26):

Method: Bi-directional sequencing of all exons and exon-intron boundaries


Limitations: Variants in the promoter region, large deletions, large duplications, or rare recombinant variants may not be detected by this method.


GJB6 (connexin 30):

Method: Polymerase Chain Reaction (PCR) followed by gel electrophoresis analysis.


GJB2 and GJB6 are analyzed serially, as follows: GJB2 is sequenced first. Reflexive GJB6 deletion analysis is performed only if one GJB2 variant is detected.  


CPT Codes

81252, 81254 (updated 2/2/16 by jconta)


Molecular Genetics

Clinical Utility

DFNB1 nonsyndromic hearing loss and deafness is characterized by congenital non-progressive, mild-to-profound sensorineural hearing impairment.  DFNB1 is inherited in an autosomal recessive manner.


Sequencing analysis of the entire coding region of the GJB2 gene detects both variants in 98% of persons with DFNB1 nonsyndromic hearing loss and deafness. Approximately 2% of individuals with DFNB1 have one identifiable GJB2 variant and one of two large deletions that include a portion of GJB6.  It is extremely rare for individuals with DFNB1 to have homozygous large deletions that include a portion of the GJB6 gene.