Spinal Muscular Atrophy, Carrier Test (Sendout)

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General Information

Lab Name
Spinal Muscular Atrophy, Carrier Test (Sendout)
Lab Code
RSMACT
Epic Ordering
Spinal Muscular Atrophy, Carrier Test (Sendout)
External Test Id
2013436
Description

Ordering Recommendation: Confirm a suspected diagnosis of spinal muscular atrophy (SMA) and quantify SMN2 copy number for treatment purposes in affected individuals. Use for prenatal or preconception carrier screening for SMA in the general population, carrier screening for the reproductive partner of a known SMA carrier, and carrier screening for parents of a child with a deletion of the SMN1 gene or other family history of SMA.

Optional Order Information:

  • Indicate the reason for testing (routine preconception/prenatal carrier screening or symptoms) at order entry in Epic.
  • For orders not submitted in Epic, providers may submit a completed ARUP SMA Testing Patient History Form (not required for testing).
References
Forms & Requisitions
Synonyms
2013436, SMA, SMA Carrier Testing, SMA Copy Number Analysis, SMA Dosage Testing, SMA Type 1, SMN gene, SMN1 exon 7, SMN1 gene, survival motor neuron gene
Components

Interpretation

Method

Multiplex probe ligation-dependent amplification (MLPA)

Reference Range
See individual components
Ref. Range Notes
Result Interpretation
1 copy of SMN1 Individual is a carrier of SMA
2 copies of SMN1 with absence of linked variant Carrier risk is reduced, but not eliminatedᵃ
2 copies of SMN1 with presence of linked variant Increased risk of being a silent carrierᵇ
3 or more copies of SMN1 Carrier risk is significantly reduced, but not eliminatedᶜ

a. Both SMN1 copies may be on the same chromosome, or a pathogenic sequence variant may be present on one chromosome.

b. Both SMN1 copies may be on the same chromosome with no copies on the other chromosome.

c. Linked variant is not clinically relevant.

Residual carrier risk for SMA depends on an individual’s genetic admixture.

Interferences and Limitations

Limitations:

  • Diagnostic errors can occur due to rare sequence variations.
  • Single base pair substitutions, small deletions/duplications, and regulatory region and deep intronic variants will not be detected.
  • This test is unable to determine:
    • Whether SMN1 copies are on the same or opposite chromosomes
    • Whether SMN1 and SMN2 copies are on the same or opposite chromosomes
References

Ordering & Collection

Specimen Type
Blood
Collection

3 mL whole blood/cord blood in LAVENDER (EDTA) top tube

Also accepted: Yellow ACD (Solution A or B)

Forms & Requisitions
Handling Instructions

Outside Laboratories:

  • Refrigerate whole blood in original collection container. Ship refrigerated.
  • Recommended: Submit a completed ARUP SMA Testing Patient History Form (optional) along with the DLMP requisition*. Orders can be processed without the ARUP form.
    • *Use client-specific requisition when available. To obtain a client-specific requisition, contact Client Support Services via email at: commserv@uw.edu.

Stability: Refrigerated (preferred): 1 month; Ambient: 1 week; Frozen: 6 months.

Quantity
requested: 3 mL EDTA or ACD whole blood
minimum: 1 mL EDTA or ACD whole blood

Processing

Processing

Refrigerate whole blood in original collection container.

Sendouts:

  • Order ARUP Test: 2013436.
  • Interfaced: Yes [Interface: 602; Department: ARPR]
  • If provided, include a copy of the SMA Patient History Form with the sample. Orders can be processed without the form.

Stability: Refrigerated (preferred): 1 month; Ambient: 1 week; Frozen: 6 months.

Performance

LIS Dept Code
Sendouts ARUP Lab (RF) (ARPR)
Performing Location(s)
Sendout ARUP Laboratories, Inc.
800-522-2787

500 Chipeta Way
Salt Lake City, UT 84108
Frequency
Performed: Varies. Reported: 7-14 days from sample receipt at ARUP Laboratories.
Available STAT?
No

Billing & Coding

CPT codes
81329
LOINC
49857-6
Interfaced Order Code
UOW5112