Spinocerebellar Ataxia Type 6 Expansion Analysis

Test Information

CACNA1A trinucleotide repeat analysis is a molecular test used to identify expanded CAG repeat size in the gene associated with spinocerebellar ataxia type 6.

Turnaround Time

21 days

CPT Code(s)






Clinical Information

Spinocerebellar ataxia type 6 is a slowly progressive form of cerebellar ataxia with initial features that include lack of coordination and balance and dysarthria. Over time, vision problems including nystagmus and double vision, dysphagia, and tremors will develop. Average age of onset is in the 40s, and the rate of progression is typically slow with a normal lifespan. SCA6 is inherited in an autosomal dominant pattern, and it is caused by a CAG trinucleotide repeat expansion in the CACNA1A gene. Repeat ranges are as follows: Normal (≤ 18), Intermediate (19), Pathogenic (≥ 20).


Triplet repeat-primed PCR

Specimen Requirements

The preferred sample type is 3-5 ml of peripheral blood collected in an EDTA (purple top) tube. Extracted DNA and saliva are also accepted for this test. Saliva samples must be submitted in an approved saliva kit. Contact the lab to receive a saliva kit or to have one sent to your patient.

Transport Instructions

The specimen should be kept at room temperature and delivered via overnight shipping. If shipment is delayed by one or two days, the specimen should be refrigerated and shipped at room temperature. Do not freeze the specimen. Samples collected on Friday can be safely designated for Monday delivery.

Prenatal Testing Information

Prenatal testing may be available in cases where one parent is known to have an expanded allele. Please contact the lab to discuss specific cases prior to sending a sample.

Have Questions? Need Support?

Call our laboratory at 1-800-473-9411 or contact one of our Laboratory Genetic Counselors for assistance.
Robin Fletcher, MS, CGC
Falecia Thomas, MS, CGC
Alex Finley, MS, CGC

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