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Deafness, Autosomal Recessive 28 (DFNB28) via the TRIOBP Gene

Summary and Pricing

Test Method

Exome Sequencing with CNV Detection
Test Code Test Copy GenesTest CPT Code Gene CPT Codes Copy CPT Codes Base Price
TRIOBP 81479 81479,81479 $990
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
11769TRIOBP81479 81479,81479 $990 Order Options and Pricing

Pricing Comments

Our favored testing approach is exome based NextGen sequencing with CNV analysis. This will allow cost effective reflexing to PGxome or other exome based tests. However, if full gene Sanger sequencing is desired for STAT turnaround time, insurance, or other reasons, please see link below for Test Code, pricing, and turnaround time information. If the Sanger option is selected, CNV detection may be ordered through Test #600.

An additional 25% charge will be applied to STAT orders. STAT orders are prioritized throughout the testing process.

Click here for costs to reflex to whole PGxome (if original test is on PGxome Sequencing platform).

Click here for costs to reflex to whole PGnome (if original test is on PGnome Sequencing platform).

The Sanger Sequencing method for this test is NY State approved.

For Sanger Sequencing click here.

Turnaround Time

3 weeks on average for standard orders or 2 weeks on average for STAT orders.

Please note: Once the testing process begins, an Estimated Report Date (ERD) range will be displayed in the portal. This is the most accurate prediction of when your report will be complete and may differ from the average TAT published on our website. About 85% of our tests will be reported within or before the ERD range. We will notify you of significant delays or holds which will impact the ERD. Learn more about turnaround times here.

Targeted Testing

For ordering sequencing of targeted known variants, go to our Targeted Variants page.


Genetic Counselors


  • Ben Dorshorst, PhD

Clinical Features and Genetics

Clinical Features

Autosomal recessive deafness 28 (DFNB28) is characterized by prelingual, bilateral, symmeterical, stable, severe to profound, sensorineural nonsyndromic hearing loss (Shahin et al. 2006). The audioprofile of most nonsyndromic hearing loss cases can be distinct, thus assisting in the development of an evaluation strategy for molecular genetic testing and in generating a prognosis on the rate of hearing loss per year (Hildebrand et al. 2008). Pure-tone audiometery of DFNB28 individuals are usually flat, indicating hearing loss at all frequencies (Riazuddin et al. 2005). Individuals diagnosed with DFNB28 generally do not present any signs of syndromic deafness, which include facial dysmorphology, night blindness, structural abnormalities involving the vestibutle, goiter, and kidney disease.


DFNB28 is an autosomal recessive hearing disorder that is caused by pathogenic sequence variants in the trio- and F-actin-binding protein (TRIOBP) gene. The TRIOBP gene is located in chromosomal region 22q13.1 and consists of 23 coding exons (Hirosawa et al. 2001). The TRIOBP gene undergoes alternative splicing, which results in three isoforms, of which the longest isoform encodes a 2,365-amino acid protein that is expressed in the cochlea, retina, and fetal brain (Riazuddin et al. 2006). Previous studies have shown that the TRIOBP protein is particularly expressed at the base of stereocilia rootlets of the outer hair cells of the cochlea and is involved in mechanoelectrical transduction of sound waves (Kitajiri et al. 2010). The TRIOBP protein directly binds to F-actin, which in turn induces actin remodeling (Seipel et al. 2000). This particular interaction provides flexibility to the stereocilia bundle by reducing structural rigidity, thereby facilitating in the transmission of mechanoelectrical signals for the perception of sound (Shahin et al. 2006). To date, about 18 pathogenic TRIOBP sequence variants have been reported, which include 15 missense/nonsense, 2 small deletions, and 1 small insertion (Human Gene Mutation Database).

Clinical Sensitivity - Sequencing with CNV PGxome

The clinical sensitivity of this test has been reported to range from 0.5% to 5%. For example, in Japan, pathogenic sequence variants in the TRIOBP gene were detected in 0.5% (7/216) of deaf patients (Miyagawa et al. 2013). In three independent research studies conducted in Iran, pathogenic sequence variants in the TRIOBP gene accounted for ~0.6% to 5% (1/20, Diaz-Horta et al. 2012; 1/144, Babanejad et al. 2012; 1/160, Bademci et al. 2015) of families with autosomal recessive nonsyndromic hearing loss.

Testing Strategy

This test provides full coverage of all coding exons of the TRIOBP gene plus 10 bases of flanking noncoding DNA in all available transcripts along with other non-coding regions in which pathogenic variants have been identified at PreventionGenetics or reported elsewhere. We define full coverage as >20X NGS reads or Sanger sequencing. PGnome panels typically provide slightly increased coverage over the PGxome equivalent. PGnome sequencing panels have the added benefit of additional analysis and reporting of deep intronic regions (where applicable).

Dependent on the sequencing backbone selected for this testing, discounted reflex testing to any other similar backbone-based test is available (i.e., PGxome panel to whole PGxome; PGnome panel to whole PGnome).

Indications for Test

The ideal TRIOBP test candidates are individuals who present with prelingual, bilateral, symmetrical, stable, severe to profound, sensorineural, autosomal recessive nonsyndromic hearing loss. This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in TRIOBP.


Official Gene Symbol OMIM ID
TRIOBP 609761
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT


Name Inheritance OMIM ID
Deafness, Autosomal Recessive 28 AR 609823


  • Babanejad M. et al. 2012. American Journal of Medical Genetics. Part A. 158A: 2485-92. PubMed ID: 22903915
  • Bademci G. et al. 2015. Genetics in Medicine : Official Journal of the American College of Medical Genetics. 0: N/A. PubMed ID: 26226137
  • Diaz-Horta O. et al. 2012. Plos One. 7: e50628. PubMed ID: 23226338
  • Hildebrand M.S. et al. 2008. Genetics in Medicine. 10: 797-804. PubMed ID: 18941426
  • Hirosawa M. et al. 2001. Dna Research : an International Journal For Rapid Publication of Reports on Genes and Genomes. 8: 1-9. PubMed ID: 11258795
  • Human Gene Mutation Database (Bio-base).
  • Kitajiri S. et al. 2010. Cell. 141: 786-98. PubMed ID: 20510926
  • Miyagawa M. et al. 2013. PLoS One. 8: e71381. PubMed ID: 23967202
  • Riazuddin S. et al. 2006. American Journal of Human Genetics. 78: 137-43. PubMed ID: 16385457
  • Seipel K. et al. 2001. Journal of Cell Science. 114: 389-99. PubMed ID: 11148140
  • Shahin H. et al. 2006. American Journal of Human Genetics. 78: 144-52. PubMed ID: 16385458


Ordering Options

We offer several options when ordering sequencing tests. For more information on these options, see our Ordering Instructions page. To view available options, click on the Order Options button within the test description.

myPrevent - Online Ordering

  • The test can be added to your online orders in the Summary and Pricing section.
  • Once the test has been added log in to myPrevent to fill out an online requisition form.
  • PGnome sequencing panels can be ordered via the myPrevent portal only at this time.

Requisition Form

  • A completed requisition form must accompany all specimens.
  • Billing information along with specimen and shipping instructions are within the requisition form.
  • All testing must be ordered by a qualified healthcare provider.

For Requisition Forms, visit our Forms page

If ordering a Duo or Trio test, the proband and all comparator samples are required to initiate testing. If we do not receive all required samples for the test ordered within 21 days, we will convert the order to the most effective testing strategy with the samples available. Prior authorization and/or billing in place may be impacted by a change in test code.

Specimen Types

Specimen Requirements and Shipping Details

PGxome (Exome) Sequencing Panel

PGnome (Genome) Sequencing Panel

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2) Select Additional Test Options

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Note: acceptable specimen types are whole blood and DNA from whole blood only.
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