General population carrier screening for spinal muscular atrophy (SMA)
Carrier screening for reproductive partners of known SMA carriers
Carrier screening for parents of a child with a known deletion of the survival motor neuron 1 gene (SMN1) or other family history of SMA
SMN1 exon 7 copy number and SMN2 exon 7 copy number are determined. Also ascertains whether the g.27134T>G polymorphism is present or absent in patients found to have 2 copies of SMN1
Specimen Type
Whole Blood
Blood spot
Cultured fibroblasts
Skin biopsy
Tissue biopsy
Specimen Collection / Processing Instructions
Patient Preparation: A previous bone marrow transplant from an allogenic donor will interfere with testing. Call Mayo Clinic Laboratories for instructions for testing patients who have received a bone marrow transplant.
Specimen Type: Whole Blood (3mL)
Preferred: Lavender top (EDTA)
Acceptable: Yellow top (ACD), or any anticoagulant
Supplies: Fibroblast Biopsy Transport Media (T115)
Container/Tube: Sterile container with any standard cell culture media (eg, minimal essential media, RPMI 1640). The solution should be supplemented with 1% penicillin and streptomycin. Tubes can be supplied upon request (Eagle's minimum essential medium with 1% penicillin and streptomycin [T115])
Specimen preferred to arrive within 96 hours of collection
Unacceptable Specimen Conditions
All specimens will be evaluated by Mayo Clinic Laboratories for test suitability.
Limitations
Point mutations are undetectable by this assay. Nor can this assay definitively discriminate between 2 copies of survival motor neuron 1 (SMN1) on the same chromosome versus 2 copies on separate chromosomes for patients of most ancestries
Rare polymorphisms exist that could lead to false-negative or false-positive results. If results obtained do not match clinical findings, additional testing should be considered
Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in our interpretation of results may occur if information given is inaccurate or incomplete
Methodology
Dosage Analysis by Digital Droplet Polymerase Chain Reaction (ddPCR)
Estimated TAT
5-10 days
Retention
Whole Blood: 2 weeks
Extracted DNA: 3 months
CPT Code(s)
81329
Reference Range
An interpretive report will be provided.
Reflex Conditions
CULFB: Fibroblast Culture for Genetic Test (skin biopsy only)