In order to confirm a diagnosis, a molecular genetic blood test must be performed to confirm whether or not the child has a specific mutation in the SMN1 gene that causes spinal muscular atrophy. This test is also referred to as an SMN gene deletion test. The copy number of the SMN2 gene can also be determined.1,2 Approximately 95% to 98% of individuals with a clinical diagnosis of spinal muscular atrophy have a mutation in the SMN1 gene. The SMN gene deletion test is performed by several diagnostic laboratories. The results can be achieved in approximately 3 to 4 weeks, though this may vary by centre.2

A list of commonly used terms is available here

The first thing a doctor may notice in a baby with spinal muscular atrophy is floppiness or decreased muscle tone (hypotonia)1

Since hypotonia is a common finding in several genetic conditions, a doctor may order a congenital hypotonia panel. This will test for spinal muscular atrophy as well as myotonic dystrophy (type 1), Prader-Willi syndrome, Angelman syndrome, and maternal uniparental disomy 14.4 The turnaround time for a congenital hypotonia panel is approximately 3 weeks, though this may vary by centre.4

Arriving at a diagnosis may take some medical detective work

Because each child shows signs and symptoms at different ages and with different severity, an initial diagnosis can be delayed.5 A recent survey of parents and doctors showed that the recognition of symptoms and finding a diagnosis required numerous visits to their paediatrician and specialists.6-8

Children may receive other diagnostic tests, including additional genetic testing, electromyography, or a blood test to measure the level of creatine kinase—an enzyme that leaks out of deteriorating muscles. Unlike a genetic molecular blood test, these tests may not accurately confirm a spinal muscular atrophy diagnosis. However, they may be used to rule out other forms of muscle disease.3

Newborn screening
Although newborn screening is not yet standard practice, time to diagnosis is critical. Earlier diagnosis may help improve outcomes for children with spinal muscular atrophy.5