Spinocerebellar ataxia CAG repeat expansion panel

Information for clinical testing:

We screen for polyglutamine-coding CAG repeat expansions in the most common spinocerebellar ataxia (SCA) subtypes — SCA1, SCA2, SCA3, SCA6, SCA7 and SCA17.  For known mutations, repeat expansion tests can be ordered for individual genes.  Also, an individual test for X-linked spinal and bulbar muscular atrophy (SBMA) caused by CAG repeat expansions in the androgen receptor gene is available.

For ordering and shipping instructions, please fill-in and send with the blood sample the information/billing and DNA testing consent form.



Genomic DNA is purified from peripheral blood samples followed by gene-specific polymerase chain reaction (PCR) of the CAG repeat region using a 5′ fluorescently labeled primer and a 3′ unlabeled flanking primer. The CAG repeat number in each allele is determined by fragment length analysis on a capillary electrophoresis instrument (ABI 3730xl DNA analyzer with a GeneScan 500 LIZ Size Standard).  Expanded and homozygous alleles are confirmed by triplet-repeat primed PCR and sizing by capillary electrophoresis.

  • Disease
  • Gene Symbol
  • GeneReview


Repeat Ranges:

  • Normal
  • Intermediate
  • Expanded


  1. Print out the information/billing and DNA testing consent form for SCA repeat expansions. You and your physician must fill out the form and send it along with the blood sample.
  2. Print out the UofU_blood_shipping_instructions and take them with you to your doctor or a blood drawing laboratory.


  • CAG repeat expansion panel including SCA1, SCA2, SCA3, SCA6, SCA7 and SCA 17:          $550
  • Individual repeat expansion test for SCA1, SCA2, SCA3, SCA6, SCA7, SCA 17 or SBMA:     $400
  • Testing for family members of patients with previously detected mutations:                        $300

Please Note:

  • You are responsible for the cost of the test and payment method must accompany the sample. If you have insurance, you may be able to submit the bill for the test to your insurance company for reimbursement (CPT Codes for insurance claims, we do not bill your insurance company). Payment must be made in US dollars.
  • It is possible that we will be unable to detect a mutation in the gene. You are still responsible for paying the costs of the test.


Your physician will receive results by mail in approximately three (3) to four (4) weeks.

If you have questions about these tests, please contact Diane Dunn (Laboratory Supervisor) at (801) 585-3436 or ddunn@genetics.utah.edu.