Friedreich Ataxia, Repeat Expansion Analysis, Varies
Use
This test is useful for the molecular confirmation of clinically suspected Friedreich ataxia. It assesses for GAA trinucleotide repeat expansions within the FXN gene to confirm a molecular diagnosis. Friedreich ataxia is a progressive hereditary ataxia characterized by gait and limb ataxia, dysarthria, and sensory loss, often accompanied by cardiomyopathy and diabetes mellitus. The majority of individuals affected by Friedreich ataxia exhibit homozygous GAA trinucleotide repeat expansions in intron 1 of the FXN gene. This analysis is significant for categorizing the size of the repeat expansions, which correlates with the onset and severity of the disease.
Special Instructions
All prenatal specimens must be accompanied by a maternal blood specimen; order MATCC / Maternal Cell Contamination, Molecular Analysis, Varies on the maternal specimen, as this must be a different order number than the prenatal specimen. It is strongly recommended that patients undergoing genetic testing receive genetic counseling. New York Clients-Informed consent is required, and it should be documented on the request form or electronic order that a copy is on file.
Limitations
The assay will not detect nonrepeat expansion variants such as sequence variants, deletions, and duplications. Errors in test interpretation may occur if the provided information is inaccurate or incomplete. Bone marrow transplants from allogenic donors will interfere with testing, as results may not reflect true GAA repeat sizes in other tissues. Some prenatal specimen tests will add additional charges for culture, as well as maternal cell contamination studies. The GAA-repeats size in peripheral blood specimens may not fully represent the size in other tissues due to somatic mosaicism.
New York Approved
Methodology
PCR-based (PCR)
Biomarkers
LOINC Codes
- 21762-0
- 50397-9
- 21762-0
- 69047-9
- 42349-1
- 31208-2
- 85069-3
- 62364-5
- 18771-6
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.
Patient Preparation
A previous bone marrow transplant from an allogenic donor will interfere with testing.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 4 days |
| Refrigerated | 4 days |
| Frozen | 4 days |