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Genetic repeat expansion analysis of C9ORF72 (hexanucleotide repeat) in DNA

Published: August 9, 2026Updated: August 16, 2026

This test checks for abnormal expansions of a specific DNA sequence in the C9ORF72 gene, which may be linked to certain neurodegenerative diseases.

Quick summary

["This test helps assess risk for rare genetic disorders affecting movement and brain function."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
81847-6
Short code
C9orf72 GGGGCC repeat analysis Amn
Synonyms
C9orf72 GGGGCC repeat analysis Amn
Category
chemistry
Sample
fluid
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
molgen
CPT
86038
Specimen volume
2-5 mL
Stability
Room temperature: 2h, Refrigerated: 24h
Hemolysis max
300
TAT
4–24 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms of a neurodegenerative disorder, a family history of such conditions, or if genetic counseling suggests a possible C9ORF72 mutation. It’s also used in research or clinical trials for specific genetic testing protocols.

What to Expect Before the Test

You’ll need a blood sample drawn from a vein. No special preparation is typically required, but your provider may ask you to avoid certain medications or activities for a short time before testing.

What the Test Results Mean

Results are compared to known ranges of normal and expanded repeats. Abnormal expansions (usually 25–230 repeats) may indicate an increased risk for diseases like frontotemporal dementia or amyotrophic lateral sclerosis (ALS).

Common Conditions Linked to This Test

This test is primarily used to diagnose or assess risk for neurodegenerative diseases caused by C9ORF72 expansions, such as familial ALS or frontotemporal dementia.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

If you have an abnormal result, it means you carry a higher risk for developing C9ORF72-related diseases. Early genetic counseling can help explain your risk, potential symptoms, and available support or research options. Results may also guide family planning discussions or genetic testing for relatives.

Short name

C9ORF72 Repeat Expansion Test

Frequently asked questions

What does a positive result mean?
A positive result means your DNA contains an unusually large number of the C9ORF72 hexanucleotide repeats, which may increase your risk of developing neurodegenerative diseases like ALS or frontotemporal dementia. This does not confirm a diagnosis but indicates a genetic predisposition.
How soon can I expect results?
Results are typically available within 1–2 weeks after your sample is processed. Your healthcare provider will contact you directly to discuss the findings.
Can this test be used for prenatal or carrier screening?
Yes, this test can be used for prenatal screening in high-risk pregnancies or to determine if you are a carrier of the mutation in family planning contexts. Genetic counseling is strongly recommended before proceeding.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy