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Test Code AIHL Aminoglycoside-Induced Hearing Loss, Targeted Variant Testing, Droplet Digital PCR, Varies


Ordering Guidance


The preferred genetic test for diagnosis in individuals with suspicion of syndromic or non-syndromic hereditary hearing loss is HHLP / AudioloGene Hereditary Hearing Loss Panel, Varies.



Shipping Instructions


Specimen preferred to arrive within 96 hours of collection.



Specimen Required


Patient Preparation: A previous bone marrow transplant from an allogenic donor will interfere with testing. Call 800-533-1710 for instructions for testing patients who have received a bone marrow transplant.

 

Specimen Type: Whole blood

Container/Tube:

Preferred: Lavender top (EDTA) or yellow top (ACD)

Acceptable: Any anticoagulant

Specimen Volume: 3 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send specimen in original tube.

Specimen Stability Information: Ambient/Refrigerated/Frozen

Additional Information: To ensure minimum volume and concentration of DNA is met, the preferred volume of blood must be submitted. Testing may be canceled if DNA requirements are inadequate.

 

Specimen Type: Saliva

Patient Preparation: Patient should not eat, drink, smoke, or chew gum 30 minutes prior to collection.

Supplies: Saliva Collection Kit (T786)

Specimen Volume: 1 swab

Collection Instructions: Collect and send specimen per kit instructions.

Specimen Stability Information: Ambient


Forms

1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing (Spanish) (T826)

2. Molecular Genetics Hereditary Hearing Loss Patient Information

3. If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.

Useful For

Identification of individuals who may be at risk for aminoglycoside-induced hearing loss (AIHL)

 

Establishing a diagnosis of late-onset sensorineural hearing loss associated with aminoglycoside exposure

 

Identifying mitochondrial variants associated with AIHL, allowing for predictive testing of at-risk family members

Method Name

Droplet Digital Polymerase Chain Reaction (ddPCR)

Reporting Name

Aminoglycoside-Induced Hearing Loss

Specimen Type

Varies

Specimen Minimum Volume

See Specimen Required

Specimen Stability Information

Specimen Type Temperature Time Special Container
Varies Varies

Reject Due To

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Clinical Information

Aminoglycosides (tobramycin, streptomycin, and gentamicin, etc) are a group of broad-spectrum antibiotics commonly prescribed for infections caused by Gram-negative bacteria. In the United States alone, approximately 4 million courses of aminoglycosides are administered each year with approximately 2% to 5% of patients treated developing clinically significant hearing loss. Mitochondrial gene RNR1 (MT-RNR1) variants m.1555A>G and m.1494C>T are the most common variants associated with aminoglycoside-induced ototoxicity. Hearing loss associated with aminoglycoside exposure can occur even after a single dose and may be bilateral, irreversible, and often severe to profound. Avoidance of aminoglycoside antibiotics reduces the risk of developing hearing loss for individuals carrying one of these 2 variants.

 

The severity and onset of hearing loss in individuals with the associated pathogenic mitochondrial variants range from profound congenital deafness to mild to moderate late-onset hearing loss. Evidence demonstrates that this variance can often be explained by variant load in an individual. In contrast to variants in nuclear genes, which are present in either 0, 1, or 2 copies, mitochondrial variants can be present in any fraction of the total organelles, a phenomenon known as heteroplasmy. Penetrance of hearing loss without exposure to aminoglycosides is thought to be a function of the degree of heteroplasmy, with a correlation between higher fraction of altered mitochondria and higher penetrance. Hearing loss is believed to be 100% penetrant in homoplasmic individuals who receive aminoglycoside antibiotics.

Reference Values

An interpretive report will be provided.

Interpretation

An interpretive report will be provided.

Cautions

Clinical Correlations:

Test results should be interpreted in context of clinical findings, family history, and other laboratory data. Misinterpretation of results may occur if the information provided is inaccurate or incomplete.

 

If testing was performed because of a clinically significant family history, it is often useful to first test an affected family member. Detection of a reportable variant in an affected family member would allow for more informative testing of at-risk individuals.

 

Technical Limitations:

This assay will not detect all variants or genes that cause mitochondrial nonsyndromic hearing loss and deafness. Therefore, the absence of a detectable variant does not rule out the possibility that an individual is a carrier of or affected with mitochondrial non-syndromic hearing loss and deafness.

 

Some individuals who are a carrier or have a diagnosis of mitochondrial nonsyndromic hearing loss and deafness may have a variant that is not identified by this assay. The absence of a variant, therefore, does not eliminate the possibility of a hereditary hearing loss disorder. For predictive testing of asymptomatic individuals, it is important to first document the presence of a gene variant in an affected family member.

 

Of note, absence of the mitochondrial variants MT-RNR1 m.1494C>T or MT-RNR1 m.1555A>G does not rule out the presence of these variants below the limits of detection of this assay (<5% heteroplasmy).

 

Rare alterations exist that could lead to false-negative or false-positive results. If results obtained do not match clinical findings, additional testing should be considered.

Day(s) Performed

Monday through Saturday

Report Available

1 to 7 days-Specimens must arrive in the performing laboratory by 12 p.m. for the report to be available 1 day from specimen receipt.

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

81401

LOINC Code Information

Test ID Test Order Name Order LOINC Value
AIHL Aminoglycoside-Induced Hearing Loss In Process

 

Result ID Test Result Name Result LOINC Value
609786 Specimen 31208-2
609787 Source 31208-2
609788 Result Summary 50397-9
609789 Result 82939-0
609790 Interpretation 69047-9
609791 Additional Information 48767-8
609792 Method 85069-3
609793 Disclaimer 62364-5
609794 Released By 18771-6