Laboratory Services

Spinal Muscular Atrophy Carrier Screening, Deletion/Duplication Analysis, Varies

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Updated Test Information:

Test Description
Spinal Muscular Atrophy Carrier Screening, Deletion/Duplication Analysis, Varies

Spinal Muscular Atrophy Type I; SMA1; SMAI; SMA Infantile Acute Form; Muscular Atrophy, Infantile; Severe Infantile Acute Spinal Muscular Atrophy; Spinal Muscular Atrophy-1; Spinal Muscular Atrophy, Type II; SMA2; SMAII; Muscular Atrophy, Spinal, Intermediate Type; Muscular Atrophy, Spinal, Infantile Chronic Form; Infantile Chronic Spinal Muscular Atrophy; Spinal Muscular Atrophy-2; Spinal Muscular Atrophy, Type III; SMA3; SMAIII; Muscular Atrophy, Juvenile; Kugelberg-Welander Syndrome; KWS; Spinal Muscular Atrophy, Mild Childhood and Adolescent Form; Spinal Muscular Atrophy-3; Spinal Muscular Atrophy, Type IV; SMA4; SMAIV; Spinal Muscular Atrophy, Adult Form; Spinal Muscular Atrophy, Proximal, Adult, Autosomal Recessive; Adult-Onset SMA; Spinal Muscular Atrophy-4; SMA carrier screening

Test ID
General Information

Useful for:

  • 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

    • Collection Instructions:

      • Invert several times to mix blood

      • Send specimenin original tube

    • Specimen Stability: Ambient (preferred)/Refrigerated

  • Specimen Type: Blood spot (5 spots)

    • Preferred: Collection card (Whatman Protein Saver 903 Paper)

    • Acceptable: Ahlstrom 226 filter paper, or Card-Blood Spot Collection Filter paper (T493)

    • Collection Instructions:

      • An alternative blood collection option for a patient >1 year of age is finger stick

      • Let blood dry on the filter paper at ambient temperature in a horizontal position for 3 hours

      • Do not expose specimen to heat or direct sunlight

      • Do not stack wet specimens

      • Keep specimen dry

      • See Blood Spot Collection Instructions for details

    • Specimen Stability: Ambient (preferred)/Refrigerated

  • Specimen Type: Cultured fibroblasts

    • Container/Tube: T-75 or T-25 flask

    • Specimen Volume: 1 full T-75 or 2 full T-25 flasks

    • Specimen Stability: Ambient (preferred)/Refrigerated <24 hours

  • Specimen Type: Skin biopsy

    • 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 Volume: 4-mm punch

    • Specimen Stability: Refrigerated (preferred)/Ambient

  • Specimen Type: Tissue biopsy

    • Supplies: Muscle Biopsy Kit (T541)

    • Collection Instructions: See Muscle Biopsy Specimen Preparation

    • Additional Information: Muscle Biopsy Shipping Kits (T541) are available

    • Specimen Volume: 10-80 mg Specimen

    • Specimen Stability: Frozen (preferred)/Ambient/Refrigerated

Additional Processing Details

Specimen preferred to arrive within 96 hours of collection

Unacceptable Specimen Conditions

All specimens will be evaluated by Mayo Clinic Laboratories for test suitability.


  • 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


Dosage Analysis by Digital Droplet Polymerase Chain Reaction (ddPCR)

Estimated TAT

5-10 days


  • Whole Blood: 2 weeks

  • Extracted DNA: 3 months

CPT Code(s)


Additional Information
Minimum Sample Volume

  • Blood: 1 mL

  • Tissue Biopsy: 200 mg

Reference Range

An interpretive report will be provided.

Reflex Conditions

  • CULFB: Fibroblast Culture for Genetic Test (skin biopsy only)

Performing Lab


LOINC Code(s)

50397-9, 49857-6, 69047-9, 48767-8, 31208-2, 31208-2, 18771-6