Overview

Spinal Muscular Atrophy Test

also known as: Congenital Axonal Neurotherapy, SMN1 Copy-number Analysis

What is Spinal Muscular Atrophy Test?

SMA (spinal muscular atrophy) is a disease that robs people of every physical activity by affecting the motor nerve cells in the spinal cord, taking away the ability to walk, eat, or breathe. It is the number one genetic cause of death for infants. There are 4 types of SMA’s they are I, II ,III and IV, it depends upon the age and the physical milestone achieved during that age. It is diagnosed through Genetic testing, which is done through a blood sample.

Preparation for Spinal Muscular Atrophy Test

No special preparation is required for these tests, Wearing a short sleeve or sleeveless shirt or T-shirt will be helpful for the technicians to draw blood from the veins.

Uses of Spinal Muscular Atrophy Test

This test is used to confirm whether an infant or toddler is affected by
SMA (Spinal Muscular Atrophy) or not.
It helps us understand which type of SMA the infant or toddler is affected
by.
Type I : Appears in babies when they are 6 months old and is found to be
severe.They rarely survive beyond a few years.
Type II: Appears in babies when they are 7-18 months old and is less
severe when compared to type I. Doesn’t affect much and the child can
live a longer life.
Type III: Appears after they are 18 months old, and it is the least severe
type. Doesn’t affect life expectancy.
Type IV: Appears in Adults and causes mild problems only.

Procedure for Spinal Muscular Atrophy Test

For the blood to be drawn, at first the area is cleansed with an antiseptic and tourniquet is placed around the upper arm for pressure. A needle is inserted into the vein and blood is drawn and collected in a vial.

Now, the tourniquet is removed and the patient is provided with cotton balls to prevent further bleeding. The collected blood sample is taken for Genetic testing.

Limitations of Spinal Muscular Atrophy Test

This copy number analysis does not detect individuals who are carriers of SMA as a result of either two (or very rarely three) copies of the SMN1 gene on one chromosome and the absence of the SMN1 gene on the other chromosome; or germline mosaicism; or small intragenic mutations within the SMN1 gene; or mutations in genes other than SMN1. False-positive results or false-negative results may occur for reasons that include genetic variants, blood transfusions, bone marrow transplantation, erroneous representation of family relationships, or contamination of a fetal sample with maternal cells.

Specimen Requirements

Specimen

Whole blood, cultured amniotic fluid, or cultured chorionic villus sample (CVS)

Volume

Adults: 10 mL whole blood; 30 mL whole blood if ordering multiple tests. Amniotic fluid: One T-25 flask of confluent cells. CVS: One T-25 flask of confluent cells. If cultured at another facility please maintain back-up cultures.

Container

Whole blood: Yellow-top (ACD-A) tube (preferred) or lavender-top (EDTA) tube. Amniotic fluid: T-25 flasks CVS: T-25 flasks.