Technique simplifies, accelerates newborn screening process
New method for analyzing blood samples for SMA has 100% accuracy, study asserts
Researchers in Turkey have developed a new method for screening newborn blood samples for mutations associated with spinal muscular atrophy (SMA).
Compared with standard techniques, the new method showed 100% accuracy for detecting SMA-positive and negative samples, they said.
The scientists believe their approach, which is simpler and involves fewer technical steps compared with established techniques “can be a very useful program for a country’s health and economy in the long run.”
The study, “A new line method; A direct test in spinal muscular atrophy screening for DBS,” was published in Molecular Genetics & Genomic Medicine.
Several countries, including the U.S., have begun to adopt newborn screening (NBS) programs for SMA that offer the possibility of diagnosing the disease immediately at birth, sometimes before symptoms are observed.
Via a small heel prick, a drop of blood is collected from a newborn infant. From that dried blood sample (DBS), standard techniques involve extracting the DNA and screening it for the genetic defect that causes SMA.
The most common types of SMA are caused by mutations in both copies of the SMN1 gene. In about 95% of cases, this mutation involves the deletion of a protein-coding portion of the gene. NBS is designed to detect that exon 7 deletion.
Current methods allegedly slower, less accurate
However, there are a number of technical challenges involved with current screening methods, including the need for the DNA extraction step, which slows the process and makes it more error-prone, according to the scientists.
As such, a team of researchers at Turkish-based SNP Biotechnology and Turkish Universities developed a simplified test for detecting the exon 7 deletion. In the test, a dried blood spot (DBS) from a newborn can be analyzed directly via a technique called real-time polymerase chain reaction (PCR) without the need to first extract the DNA.
The new method involves placing a DBS punch into a real-time PCR plate well, adding a specific solution into each well, and then run the real-time PRC. The researchers used a smaller DBS punch size to minimize the unwanted effects of DBS paper and blood proteins on the PCR reaction.
The diagnostic accuracy of their new method was evaluated in DBS from 580 newborns screened at a hospital in Turkey, as well as 50 additional DBS from whole blood samples collected in a previously published study.
The 580 DBS from newborns all returned as normal, meaning no SMA-causing mutation was detected. A total of 50 random samples also were analyzed with gold-standard screening approaches, and all came back negative as well.
Among the 50 samples genetically analyzed in the previous study with standard methods, 20 were identified correctly as having the SMA-associated exon 7 deletion with the new method, and the remaining 30 as normal.
As such, the new method “was considered as successful and validated,” the researchers wrote.
The scientists believe their approach overall “will seriously diminish time-consuming steps, lab errors, cost and additional laborious problems such as sample recording and tracking.”
Many more samples can be evaluated rapidly
Moreover, a large number of samples can be evaluated rapidly; the test takes only a little more than an hour to run.
“Many countries can effortlessly use this user-friendly … system and reduce a severe financial burden on their national budgets because the [method] can be run without many special reagents [ingredients], kits and trained personnel,” the researchers wrote.