• In a new study, researchers measured levels of a potential biomarker — a molecule used to measure disease — in children with and without spinal muscular atrophy (SMA).
• The authors found that levels of this biomarker in the blood were higher in people with more severe cases of SMA.
• In the future, the biomarker could be used to track SMA severity over time or determine whether treatments are working.

In a new study, researchers described a blood test that could help doctors better understand SMA severity in children. The results, published in September in the journal Annals of Clinical and Translational Neurology, show how doctors could track SMA over time or determine whether a new treatment is working.

The authors studied a potential SMA biomarker. A biomarker is a molecule found in the body that can serve as a sign of good or poor health. Biomarkers are often used to assess disease. For example, biomarker levels may change if a health condition develops, if symptoms improve, or if a treatment is effective at controlling the disease.

In the study, researchers wanted to find a biomarker for SMA. They analyzed a protein called neurofilament light chain (NfL). This protein is found in the neurons (nerve cells) that carry information to and from the brain. In people with SMA, the neurons become damaged and release NfL into the surrounding fluid. Some of this protein makes its way into the bloodstream.

The authors measured levels of sNfL (NfL in the blood serum) in 18 children with SMA who were taking Spinraza (nusinersen). They also assessed sNfL levels in 97 children without SMA.

The study authors identified a couple of key findings. First, sNfL could serve as a sign of SMA. Children with SMA had higher levels of sNfL than children without the condition.

Additionally, sNfL could be used as a biomarker to measure SMA severity. How severe this condition is depends on how many copies a person has of the SMN2 gene. People with more SMN2 copies tend to have less severe disease. In the study, researchers found that children with more SMN2 copies had lower levels of sNfL and fewer symptoms. This blood test may be able to tell doctors whether a person has more or less severe SMA.

The study authors also wanted to know whether sNfL could predict a child’s response to treatment. Drugs like nusinersen do not always work equally well for everyone. The authors found that among young children with two copies of the SMN2 gene, sNfL levels decreased after nusinersen treatment. These children, who all had SMA type 1, also experienced better motor function as the biomarker levels dropped. However, among older children with multiple SMN2 copies and SMA types 2 or 3, sNfL levels stayed stable.

Overall, the researchers found that sNfL could be used as a biomarker that signals the severity of a person’s SMA. Levels of sNfL could possibly be measured regularly to track SMA over time or show response to treatment. This could help doctors learn more about a child’s disease.