Spinal Muscular Atrophy (SMA) Copy Number Analysis, Fetal
Also known as: SMA DD FE
Use
Spinal muscular atrophy (SMA) is a lethal genetic disorder primarily affecting children, characterized by muscle atrophy and weakness, respiratory issues, and joint deformities. This prenatal diagnostic test is essential for detecting the presence or absence of the SMN1 gene, which is responsible for the condition. The test identifies the deletion or conversion mutations in the SMN1 gene that result in SMA. Also, the copy number of the SMN2 gene is reported, which is known to influence disease severity due to its production of motor neuron survival protein, albeit less than SMN1. Testing is recommended when both parents are carriers or have a family history of SMA.
Special Instructions
A complete Fetal Molecular Testing Patient History Form and Informed Consent for Genetic Testing (required for NY patients) must accompany the specimen. Cultured amniocytes or CVS must reach 80 percent confluence before submission, with backup cultures retained at the client's site. If samples do not meet the minimum confluence, ARUP will perform Cytogenetics Grow and Send, which incurs additional costs. Ensure specimens reach the lab within 48 hours to maintain cellular viability for accurate results.
Limitations
The test cannot detect single base substitutions, small indels, regulatory region, and intronic variants. SMN2 copies beyond three are challenging to differentiate reliably. The test cannot ascertain the chromosomal phase of SMN1 or SMN2 copies, necessitating caution in interpreting results. Diagnostic errors due to rare sequence variations can occur, and some pathogenic variants outside the targeted exons may go undetected. Genetic consultation is advised due to these limitations.
New York Approved
Methodology
Other
Biomarkers
LOINC Codes
- 59266-7
- 66746-9
- 75325-1
- 35462-1
- 54449-4
Result Turnaround Time
9-10 days
Related Documents
For more information, please review the documents below
Specimen
Cultured Cells
Volume
Not provided
Minimum Volume
Not provided
Container
Two T-25 flasks at 80 percent confluence
Collection Instructions
Transfer cultured amniocytes or CVS to T-25 flasks, ensure 80 percent confluence before sending to ARUP.
Storage Instructions
Keep at room temperature, and must arrive within 48 hours due to viability concerns.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 48 hours |
| Refrigerated | Unacceptable |
| Frozen | Unacceptable |