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How is SMA diagnosed?

If SMA is suspected, a diagnosis can be confirmed with a genetic blood test.

Testing for a missing SMN1 gene

SMA is diagnosed using a blood test called an SMN gene deletion test. The test confirms whether or not an individual has the SMN1 gene mutation that causes SMA and can determine the number of SMN2 gene copies an individual has.1

The SMN gene deletion test may be ordered by a paediatrician or neurologist and is performed in pathology labs. It can take anywhere between 3 days to 3 weeks to receive the results. 

 

Arriving at an SMA diagnosis may take some medical detective work

Because the signs and symptoms of SMA are not highly specific and may occur at different ages and with different severity, an initial diagnosis can be delayed. To help narrow down the diagnosis, healthcare providers may use other diagnostic tests to rule out other forms of muscle disease. These include:2

  • additional genetic testing
  • electromyography (a diagnostic technique that measures electrical activity in the muscle) 
  • a blood test to measure creatine kinase (an enzyme that leaks out of deteriorating muscles).

The journey from conception to diagnosis and treatment is typically complex.2

 

References
  1. Darras B. Pediatr Clin N Am 2015; 62: 743–66.
  2. Wang CH et al. J Child Neurol 2007; 22: 1027–49.