Spinocerebellar Ataxia Type 1 Repeat Analysis
Use
This test is indicated for individuals with suspected spinocerebellar ataxia type 1 (SCA1), including those with a family history of SCA1, to determine risk, support differential diagnosis among ataxias, and guide medical, disability, or genetic counseling decisions. It analyzes the CAG trinucleotide repeat region in the ATXN1 gene, where repeat length correlates with age of onset and disease progression (anticipation phenomenon).
Special Instructions
Orderable via the Neurology Test Requisition Form under test code TH84. Samples must follow standard GeneDx specimen requirements. Consult the Neurology panel PDF for consolidation of repeat expansion tests. No reflex tests indicated.
Limitations
This assay examines only the CAG repeat region of ATXN1 and does not detect other variant types. Interpretation may be affected by CAT interruption status. The test is diagnostic for the mechanism described but rare primer‐site mutations, probe failures, or sample issues may lead to errors. Results should be interpreted alongside clinical presentation, family history, and other laboratory data.
Methodology
PCR-based (PCR)
Biomarkers
Result Turnaround Time
10 days
Related Documents
For more information, please review the documents below
Specimen
Whole Blood
Volume
Prefer two 5 mL EDTA (lavender‐top) tubes
Minimum Volume
0.7 mL EDTA whole blood
Container
EDTA (lavender‐top) tube
Collection Instructions
Collect two 5 mL whole blood in EDTA tube; min 0.7 mL acceptable.
Storage Instructions
Store refrigerated; ship next‐day air (no Saturday delivery).
Causes for Rejection
Serum; frozen or severely hemolyzed blood; clotted blood
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | Ambient up to 7 days |
| Refrigerated | 2 weeks |
| Frozen | Unacceptable |