Spinocerebellar Ataxia Type 7 Repeat Analysis
Use
SCA7 is a neurodegenerative disorder typically presenting with adult-onset vision concerns or poor coordination, and infantile-onset with hypotonia, developmental delay, and retinal degeneration. Expanded CAG repeats in ATXN7 (≥37 repeats) are fully penetrant and pathogenic; 34–36 repeats are associated with incomplete penetrance and milder phenotype with anticipation across generations. Alleles with >100 repeats require Southern blot and are not resolved by this assay. These features establish the clinical utility of identifying CAG repeat expansions in ATXN7 for diagnostic confirmation.
Special Instructions
Not provided.
Limitations
Accuracy of repeat sizing is ±2 repeats for ≤50 repeats and ±5 repeats for 51–100 repeats. Alleles with >100 repeats cannot be precisely sized by this test and require Southern blot analysis. No ability to detect other variant types beyond CAG repeat expansions. Results must be interpreted in clinical context; rare diagnostic errors may occur due to primer/probe binding site mutations or polymorphisms.
Methodology
PCR-based (PCR)
Biomarkers
ATXN7
Gene
Result Turnaround Time
14 days
Related Documents
For more information, please review the documents below
Specimen
Whole Blood
Volume
2 x 5 mL
Minimum Volume
0.7 mL
Container
EDTA lavender‑top tube
Collection Instructions
Collect two 5 mL whole blood EDTA (lavender top) tubes; transport at room temperature or refrigerated.
Storage Instructions
Store specimen refrigerated if not shipped same day; ambient temp OK up to 7 days, refrigerated up to 2 weeks; frozen unacceptable.
Causes for Rejection
Frozen or severely hemolyzed blood; serum
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | Up to 7 days |
| Refrigerated | Up to 2 weeks |
| Frozen | Unacceptable |
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