Huntington Disease (HTT) Genetic Testing (Repeat Expansion)
Use
Huntington disease (HD) is a neurodegenerative disease of mid-life onset that produces choreic movements and cognitive decline, often accompanied by psychiatric changes. The disease is caused by an expansion of the CAG repeats in 3-5 out of 100,000 individuals. However, the prevalence of HD exceeds 15 per 100,000 in some populations, mostly of Western European origin. Juvenile-onset HD occurs in approximately 5% of affected patients, is rapidly progressive, and presents with rigidity, spasticity, and intellectual decline before the age of 20 years. The symptoms result from the selective loss of neurons, most notably in the caudate nucleus and putamen, and there is currently no effective treatment.
Special Instructions
Not provided.
Limitations
False positive or negative results may occur due to factors such as rare genetic variants, allele dropout, blood transfusions, or mislabeled samples. Repeat sizes greater than the maximum reportable range are noted as greater than the largest reportable repeat size. Specific nucleotide repeat expansions cannot be assessed beyond the described maximum limits, e.g., alleles with more than 100 repeats in the HTT gene.
Methodology
PCR-based (Repeat-primed PCR)
Biomarkers
Result Turnaround Time
12-14 days
Related Documents
For more information, please review the documents below
Specimen
Whole Blood
Volume
4 mL
Minimum Volume
2 mL
Container
lavender-top (EDTA) tube
Storage Instructions
Maintain specimen at room temperature or refrigerate at 4°C. Do not freeze.
Causes for Rejection
Frozen or hemolyzed specimen; quantity not sufficient for analysis; improper container
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 14 days |
| Refrigerated | 30 days |
| Frozen | do not freeze |
Other tests from different labs that may be relevant