C9orf72 Hexanucleotide Repeat, Molecular Analysis, Varies
Use
This test is used for the molecular confirmation of clinically suspected cases of c9FTD/ALS, frontotemporal dementia (FTD), or amyotrophic lateral sclerosis (ALS). It is also utilized for presymptomatic testing of individuals with a family history of c9FTD/ALS and a documented expansion in the C9orf72 gene. A significant number of familial cases of ALS and FTD are attributed to a large hexanucleotide repeat expansion (GGGGCC) in the C9orf72 gene. The presence of hundreds to thousands of repeats is typically associated with disease, while normal individuals have fewer than 20 repeats.
Special Instructions
Not provided.
Limitations
The test does not assess methylation status of the C9orf72 gene. Results may be impacted by somatic mosaicism, where repeat sizes in the blood may not reflect other tissues. The test may yield false negatives if rare variants occur in PCR primer binding regions. Sequence variants downstream of the C9orf72 repeat region might interfere with results. The assay might not detect somatic mosaic mutations below its detection limit of approximately 5%.
New York Approved
Methodology
PCR-based (PCR)
Biomarkers
No genes
Gene
LOINC Codes
- 81846-8 - C9orf72 GGGGCC repeat analysis Bld/T
- 50397-9 - Mol dx interp Bld/T Ql
- 77635-1 - C9orf72 GGGGCC Rpt EntNum Bld/T
- 69047-9 - Geneticist review
- 42349-1
- 31208-2 - Specimen source
- 18771-6 - Provider signing name
- 85069-3 - Lab test method
Result Turnaround Time
21-28 days
Related Documents
For more information, please review the documents below
Specimen
Whole Blood
Volume
3 mL
Minimum Volume
Not provided
Container
Lavender top (EDTA) or yellow top (ACD)
Collection Instructions
Invert several times to mix blood. Send whole blood specimen in original tube. Do not aliquot. Whole blood collected postnatal from an umbilical cord is also acceptable.
Patient Preparation
A previous bone marrow transplant from an allogeneic donor will interfere with testing.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 4 days |
| Refrigerated | 4 days |
| Frozen | 4 days |