Lack of Awareness, Screening Slows SMA Diagnosis in Infants

Spinal muscular atrophy (SMA), a genetic motor neuron disorder characterized by progressive muscular atrophy and weakness, has seen disease-modifying treatments approved and definitive genetic testing developed in recent years. Early diagnosis and treatment in infants is a key aspect of slowing disease progression and saving lives, but research published in BMC Pediatrics suggests there is much room for improvement in pediatricians’ awareness, patient screening, and referral patterns for SMA.

In recent years, disease-modifying treatments for SMA have become available. There are currently 3 FDA-approved therapies—nusinersen, onasemnogene abeparvovec-xioi, and risdiplam. But early diagnosis and intervention is vital to prevent severe and permanent neuron damage.

Among the 4 most common types of SMA, the 3 that affect patients the most are all typically diagnosed before 3 years of age. With Type I SMA, the most severe and common of these 4, irreversible denervation can start within just 3 months of age. Patients with this type of SMA typically require invasive supportive care as symptoms progress and lose roughly 90% of motor units by 6 months of age. They are generally unable to sit independently before treatment. But recent literature has shown that these infants are not diagnosed until a mean age of 6.3 months, after most of the damage has already been done, the study authors note.

The symptoms of Type I SMA begin at about 2.5 months on average, meaning there are likely missed cases that could have benefited from earlier intervention. While newborn screening for SMA is recommended in the United States, only about 68% of newborns are screened for it, the authors noted. But that’s not the only barrier.

“Given the complexity of the pediatric-specialty care interface, including delivery deficiencies, busy neurologists’ schedules, and lack of adequate health insurance, interference in the delivery of effective care coordination and referral may occur,” they wrote.

To gauge awareness and familiarity with SMA, developmental screening, and referral patterns, Cure SMA conducted 2 landmark surveys among pediatricians in 2018 and 2019.

The 2018 survey focused on awareness, diagnostic requirements, and screening tool use among physicians. The 2019 survey collected more detailed information on practices, developmental screening tool implementation, and barriers to specialist referrals. In tandem, they aimed to asses pediatricians’ comfort levels with identifying signs of neuromuscular disease (NMD) and predict whether they would immediately refer an infant to a pediatric neurologist should an infant or toddler show early signs of SMA.

A total of 21,264 pediatricians were contacted for the 2018 survey and 19,096 were contacted for the 2020 survey. The first received 300 completed responses, and the second received 600 (overall response rates of 2.3% and 4.5%, respectively). Both surveys were completed by a subset of 42 physicians.

In the 2018 survey, 52.7% of respondents correctly identified genetic testing as a requirement for a definitive diagnosis of SMA, while 31% incorrectly selected muscle biopsy as a requirement. In the 2019 survey, an even lower percentage (45%) answered correctly.

Current guidelines recommend using screening tools at well visits, although 56% of the physicians who responded to the 2018 survey reported screening at each well visit. In 2019, 37.3% of respondents reported using screening tools at all well visits. In 2019 researchers looked for associations between screening tool use and physician demographics, finding that those who had completed their training less than 10 years prior to the survey were 1.55 times more likely to use screening tools at every well visit or at the 9-, 18-, and 30-month marks compared with pediatricians with more than 10 years of experience.

When it came to identifying the early signs of NMD, 70.3% of respondents said they were comfortable, with 3.3% answering “extremely comfortable,” 18.7% “moderately comfortable,” and 48.3% “comfortable.” Those who were moderately or extremely comfortable were 1.47 times more likely to immediately refer a patient to a pediatric neurologist for evaluation. A total of 67.3% of respondents indicated familiarity with SMA, but 59.4% of that subgroup correctly identified the genetic testing requirement for diagnosis.

As far as referrals, average wait times were between 1-6 months for specialist visits with most being between 1-2 months, according to 64.2% of respondents. When ranking barriers to referral, the top 3 were insurance coverage, lack of triage at specialist offices, and lack of neurologist or pediatric neurologist within the region.

Overall, the review determined that newborn screening, early recognition of symptoms, and immediate referrals upon symptom identification remain areas where physicians can improve.

“Despite the advent of genetic screening, a definitive tool for the diagnosis of SMA, enhanced education and awareness efforts regarding early symptoms, and 3 new FDA approved disease-modifying treatments,” the authors concluded, “findings from these 2 surveys indicate continuing clinical knowledge gaps among pediatricians across sectors and experience levels, and point to potentially modifiable factors that contribute to the delay in SMA diagnosis.”

Reference

Curry M, Cruz R, Belter L, Schroth M, Lenz M, Jarecki J. Awareness screening and referral patterns among pediatricians in the United States related to early clinical features of spinal muscular atrophy (SMA). BMC Pediatr. Published online May 17, 2021. doi:10.1186/s12887-021-02692-2