Asuragen’s Lab Test Can Speed Up Diagnosis of SMA Carriers, Patients

Patricia Inacio, PhD avatar

by Patricia Inacio, PhD |

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Asuragen’s lab test for spinal muscular atrophy (SMA) is as robust and accurate at identifying carriers of the disease and diagnosing patients as more traditional methods, a study shows.

The diagnostic test — called AmplideX PCR/CE SMA Plus Kit — was validated independently in four labs and showed over a 97% accuracy overlap with other methods, which are more laborious and time-consuming.

“Our validation results demonstrate that the AmplideX Kit not only produces quality results, but it does so using a fast, flexible format that can be easily implemented — at a time when efficient assays and lab operations are more important than ever,” Vivianna M. Van Deerlin, MD, PhD, from the University of Pennsylvania Perelman School of Medicine, one of the labs involved in the study, said in a press release.

The results were published in The Journal of Molecular Diagnostics in a study, titled “Multisite Evaluation and Validation of a Sensitive Diagnostic and Screening System for Spinal Muscular Atrophy that Reports SMN1 and SMN2 Copy Number, along with Disease Modifier and Gene Duplication Variants.”

SMA is caused by mutations in the SMN1 gene, which contains the information for the SMN protein, essential for the survival of motor neurons, or nerve cells. It is an autosomal recessive disorder, meaning that for a child to develop SMA, they must inherit a copy of a mutated gene from both the mother and the father.

Some people have extra copies of a second gene called SMN2, which also encodes for the production of the SMN protein, albeit in low amounts. Still, the number of copies of this second gene often affects the course of SMA, with more copies associated with less severe disease.

Launched in 2019, the AmplideX kit quantifies the number of copies of the SMN1 and SMN2 genes. Moreover, it can identify genetic variants associated with changes to the SMN1 gene, meaning it helps identify the so-called “silent carriers” — people who are asymptomatic for the disease but can pass on a faulty gene to their children — as well as a child’s SMN2 copy number.

Compared to other screening methods, the kit requires a small amount of DNA (20 nanograms) and is fast, taking up to a total of four hours.

“Existing methods for identifying relevant variants in the SMN1 and SMN2 genes are often cumbersome, complex, and time-consuming,” said Gary J. Latham, PhD, chief scientific officer at Asuragen, and the study’s senior author.

“We believe this kit — which analyzes all variants in a single reaction — will be important for expanding the availability of reliable results to all populations,” he said.

With the number of potential therapies for SMA increasing, a timely diagnosis is key to identify both affected children and silent carriers.

“Breakthrough molecular medicines for SMA have raised the bar for more informative and timely SMA diagnostic assays even as labs have been overwhelmed by testing for the COVID-19 pandemic,” said Deerlin.

The effectiveness of the kit was tested by four independent laboratories: the GenePhile Bioscience Laboratory in Taiwan, the University Medical Center Groningen in the Netherlands, Turku University Hospital in Finland, and the Hospital of the University of Pennsylvania, in Philadelphia, U.S.

In total, researchers analyzed 468 samples of DNA collected from blood cells (449 cases) or from amniotic cells (cells of the placenta, 19 cases).

The samples were analyzed in parallel for mutations in the SMN1 and SMN2 genes using the AmplideX kit and two traditional but more laborious methods, called multiplex ligation-dependent probe amplification and droplet digital PCR.

The results showed that the kit showed similar efficacy as the other methods, with an accuracy of 98.6% for the SMN1 gene and 97.1% for the SMN2 gene.

“Our published study demonstrates this rapid, easy-to-run IVD [in vitro diagnostics] test can be deployed across different laboratories to produce accurate and reliable data,” said Henny Lemmink, PhD, from the department of genetics at University Medical Center Groningen. “The combination of gene copy numbers, disease modifier, and silent carrier variants in a single-tube PCR test is unprecedented.”