Skip to content

Genetic Test: CAG Repeat Analysis for CACNA1A Gene (Specified Variant)

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

This test checks the number of repeated CAG sequences in the CACNA1A gene, which may be linked to certain neurological conditions.

Quick summary

This genetic test helps assess potential risks for inherited disorders affecting movement and muscle control.

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

Key facts at a glance

LOINC
49649-7
Short code
CACNA1A1
Synonyms
CACNA1A allele 1 CAG Rpt EntNum Bld/T
Category
chemistry
Sample
whole-blood
Container
EDTA (lavender/purple-top) blood collection tube for whole blood; sterile container for tissue samples
Units
N/A
Ref low
4
Ref high
20
Critical range
— – 20 N/A
Fasting
false
Population
adult
Sex
all
Age range
0–999 years
Method
molgen
CPT
81343
SNOMED
444911005
Specimen volume
5-10 mL whole blood in EDTA tube; minimum 3 mL. Tissue samples: minimum 25 mg fresh tissue or equivalent
Stability
Whole blood: Stable at room temperature (18-25°C) for up to 48 hours; refrigerated (2-8°C) for up to 7 days; frozen (-20°C or below) for long-term storage. DNA extracted from blood: stable at 2-8°C for 1 week or -20°C for long-term.
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
168–720 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you have a family history of conditions like epilepsy, ataxia, or other neurological disorders associated with CACNA1A gene mutations. It may also be used for genetic counseling or carrier screening in certain situations.

What to Expect During the Test

A simple blood sample is typically taken from a vein in your arm. The sample is then sent to a lab for genetic analysis. Results are usually available within a few weeks.

Understanding Your Results

The test measures the length of the CAG repeat sequence in the CACNA1A gene. Normal ranges vary, and abnormal findings may indicate an increased risk for neurological conditions. Consult your healthcare provider for interpretation.

Clinical Significance

Abnormal CAG repeat lengths in the CACNA1A gene can be associated with conditions such as epilepsy, cerebellar ataxia, or other movement disorders. Genetic testing helps identify carriers or individuals at higher risk for these conditions, guiding family planning and management strategies.

Reference range

Normal CACNA1A CAG repeat range: Allele 1 typically contains 4-20 CAG repeats in the coding region. Repeat expansions beyond 20 CAG repeats are associated with spinocerebellar ataxia type 6 (SCA6) and other CACNA1A-related disorders. Intermediate alleles (20-32 repeats) may have variable penetrance.N/A

Specimen: whole-blood

No special patient preparation required. Genetic counseling is recommended before and after testing. Informed consent for genetic testing may be required per institutional policy.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Abnormal results may require further genetic counseling and may influence family planning decisions or recommendations for monitoring.

Short name

CACNA1A Gene CAG Repeat Test

Frequently asked questions

What does a 'qualitative' or 'quantitative' result mean in this test?
This test is primarily quantitative, measuring the exact number of CAG repeats. The result will specify whether the repeat count is within normal ranges or if it falls into an area considered potentially concerning.
How long does it take to get my test results?
Results are typically available within 2 to 4 weeks after the sample is received by the lab. Your healthcare provider will contact you once the results are ready.
Can this test be done on saliva instead of blood?
This specific test requires a blood sample for genetic analysis. Saliva tests are not used for this particular CAG repeat analysis.
  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