Spinal Muscular Atrophy (SMA) Copy Number Analysis

Casandra

Casandra Test Code AR62096Version 1 (DRAFT)

Performing Lab

Lab ARUP LaboratoriesLab Test ID 2013436CPT Code 81329

Spinal Muscular Atrophy (SMA) Copy Number Analysis

Also known as: SMA DD

Clinical Use

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Use

The Spinal Muscular Atrophy (SMA) Copy Number Analysis is used to confirm a suspected diagnosis of spinal muscular atrophy (SMA) and quantify SMN2 copy number for treatment purposes in affected individuals. It is also used 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. SMA is characterized by progressive muscle weakness due to degeneration of the lower motor neurons. Onset ranges from before birth to adulthood and severity is highly variable.

Special Instructions

Informed consent for genetic testing is required for New York patients. Genetic counseling and informed consent are recommended for this test. Consent forms are available online. The test is performed using multiplex ligation-dependent probe amplification (MLPA).

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. SMN2 copy numbers greater than 3 may not be reliably distinguished. The test is unable to determine chromosomal phase of SMN1 or SMN2. Even if the linked variant associated with SMN1 duplication is detected, the test cannot definitively differentiate between one or more copies of SMN1 on each chromosome from two or more copies of SMN1 on one chromosome and none on the other (silent carriers).

Test Details

New York Approved