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HelpTest ID C9ORF C9orf72 Hexanucleotide Repeat, Molecular Analysis
Secondary ID
35377Useful For
Molecular confirmation of clinically suspected cases of c9FTD/ALS, frontotemporal dementia (FTD), or amyotrophic lateral sclerosis (ALS)
Presymptomatic testing for individuals with a family history of c9FTD/ALS and a documented expansion in the C9orf72 gene
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| C9FU | C9orf72, Follow Up Analysis | No | No |
Special Instructions
Method Name
Polymerase Chain Reaction (PCR)
(PCR is utilized pursuant to a license agreement with Roche Molecular Systems, Inc.)
Reporting Name
C9orf72, Molecular AnalysisSpecimen Type
VariesSpecimen preferred to arrive within 96 hours of collection.
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.
Forms:
1. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (T576) is available in Special Instructions.
2. Molecular Genetics: Congenital Inherited Diseases Patient Information (T521) in Special Instructions.
3. If not ordering electronically, complete, print, and send a Neurology Test Request Form-General (T732) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/neurology-request-form.pdf)
Specimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Varies | Ambient (preferred) | |
| Frozen | ||
| Refrigerated | ||
Clinical Information
Frontotemporal dementia (FTD) is a presenile dementia that affects the frontal and temporal lobes of the brain. Clinical presentation is variable and includes progressive changes in behavior and personality and language disturbances. Affected individuals may also exhibit extrapyramidal signs.
Amyotrophic lateral sclerosis (ALS) is a progressive neurologic disease affecting the upper and lower motor neurons. The disease is characterized by progressive spasticity, muscle wasting and paralysis, typically leading to death from respiratory failure.
ALS and FTD are now thought to represent an overlapping spectrum of disease. Recent literature has found that approximately 40% of familial ALS and FTD cases have a large hexanucleotide repeat (GGGGCC) expansion in a noncoding region of C9orf72.
Reference Values
Normal alleles: <20 GGGGCC repeats
Intermediate alleles: 20-29 GGGGCC repeats
Full penetrance: >29* GGGGCC repeats
*Alleles greater than 30 repeats are outside the reportable range for this assay and are detected using the companion Southern blot assay. There is not enough information at this time to determine if 30 repeats is the cutoff for pathogenicity.
An interpretive report will be provided.
Cautions
For predictive testing, it is important to first document the presence of the hexanucleotide repeat amplification in the C9orf72 gene in an affected family member to confirm that molecular expansion is the underlying mechanism of disease in the family.
We strongly recommend that patients undergoing predictive testing receive genetic counseling both prior to testing and after results are available.
Predictive testing of an asymptomatic child is not recommended.
Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in our interpretation of results may occur if information given is inaccurate or incomplete.
A previous bone marrow transplant from an allogenic donor will interfere with testing. Call Mayo Medical Laboratories for instructions for testing patients who have received a bone marrow transplant.
Day(s) Performed
Tuesday; 10 a.m.
Report Available
5 daysPerforming Laboratory
Mayo Medical Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.CPT Code Information
81479-Unlisted Molecular Pathology procedure
Reflex Tests
C9orf72, Follow Up Analysis
81479-Unlisted Molecular Pathology procedure