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Diagnostic Services

Genetics Lab

Spinal Muscular Atrophy Diagnostic Testing

Spinal muscular atrophy (SMA) causes progressive muscular weakness and degeneration by loss of anterior horn cells in the brain stem and spinal cord. Age of onset can vary from prenatal onset to adult onset: SMA I, with onset before six months of age; SMA II, with onset between six and 12 months; SMA III, with onset in childhood after 12 months; and SMA IV, with adult onset. Approximately 95% of individuals with SMA are homozygous for a deletion of exons 7 & 8 of the SMN1 gene. This test will only look for deletions in exons 7 & 8.

About 5% of individuals with SMA have the deletion on one allele and a point mutation on the other allele. These individuals will have normal results by this method. For individuals with a high clinical suspicion of SMA but normal test results, SMA dosage testing by MLPA is recommended.

Test Name: Spinal Muscular Atrophy
Test Code:
SMA
Test Description:
Analysis of exons 7 & 8 of the SMN1 gene.
Synonyms:
SMA, SMN1,
Indication:
This test can be used for:
1. Diagnostic testing in an individual suspected to have SMA.
2. Prenatal testing for couples at 25% risk to have a child with SMA caused by deletion in exons 7 & 8.
This technique is not appropriate for carrier testing.
Related Tests: Maternal Cell Contamination - DNA  
Maternal DNA is compared to fetal DNA to evaluate whether maternal cell contamination of the fetal sample has occurred.

SMA Deletion/Duplication Analysis  
This test is is for SMA carrier testing or reflex diagnostic testing. It is a dosage assay to assess for duplications or deletions of the SMN gene.

Clinical Links: Spinal Muscular Atrophy GeneReview
Availability:
Collected daily
Turnaround Time:
2 weeks
Methodology:
PCR
Reference Range:
Interpretive report will be provided
Requisition:
Molecular.pdf
Consent Form:
Consent For Prenatal Diagnosis By DNA Tests
Sample Requirements: Type
Whole blood: 1-3 ml lavender(EDTA) or yellow (ACD A or B) tube.
DNA: 5-10ug extracted DNA
Prenatal samples: 2 T-25 flasks cultured CVS or amniocytes.

Processing
Keep at room temperature

Shipping
Ship whole blood at room temperature, overnight. Blood samples must be received within 3 days of collection.
Samples Received:
Mon - Fri 8:00am - 5:00pm PST
Special Considerations:
For prenatal testing, maternal cell contamination must be ordered separately. Maternal blood can be shipped ahead of the cultured cells.
Cost:
Please e-mail Lab Client Services (labclientservices@seattlechildrens.org) or call at 206-987-2617 with any billing questions
CPT Code:
Please e-mail Lab Client Services (labclientservices@seattlechildrens.org) or call at 206-987-2617 with any billing questions