by Lauren Taylor from In The Cloud Copy
Nearly all babies born in the United States today are tested for a certain panel of genetic disorders within 48 hours of birth. These state-mandated screenings use a small sample of blood from the child and test for these metabolic disorders that, if left untreated, can have serious implications. Most states, including California, use a screening technology called tandem mass spectrometry (MS/MS) to analyze the babies’ blood. While this screening technique has been used for quite some time, many genomic sequencing companies are pitching to new and expecting parents that they can detect these rare metabolic disorders more accurately; but is that the case?
Genomic Sequencing vs MS/MS
A study done by scientists from UC Berkeley, UC San Francisco, and Tata Consultancy Services is diving deeper into the battle over simple testing like MS/MS and genomic sequencing to see which is more accurate and necessary. What scientists convey is that in these cases, accuracy is of utmost importance. If the test is inaccurate and falsely positive, it leads to possibly unnecessary additional testing, time, stress, and an abundance of stress of the parents. If a test is falsely negative, it can lead to serious, lifelong consequences for the baby.
The study looked at whole-exome sequencing that looked at mutations for 78 genes that can be involved in 48 different metabolic disorders. These disorders are very rare, only affecting approximately 150 of the 500,000 babies born in the state of California each year. The MS/MS screening program has been used in the state of California since 2005 and is well-established. The genes that cause the changes have mostly all been identified. The study was able to use the dried blood of babies that had been stored for years, allowing them to study babies born from July 2005 to December 2013.
The MS/MS screening that was conducted on these babies had a 99 percent accuracy rate in catching the metabolic disorders, with only a false positive of 0.2%. On the other hand, the whole-exome sequencing found only 88 percent of the babies with metabolic disorders and missed approximately 160 of the 1,334 newborns who were born with these metabolic errors in that time period. Further, the whole exome sequencing falsely identified approximately 8,000 babies each year during the study duration, which could ultimately lead to costly and stressful appointments with metabolic specialists.
Scientists looking further at the shortcoming of the whole exome sequencing believe this could be due to several factors. Scientists say that they are not certain that they have identified every gene that is associated with these conditions, so there could be additional genes as well as environmental factors that have not yet been identified. Further, the conditions are incredibly rare, so they have not been well studied. Scientists also said that the great diversity in the genetic backgrounds of babies born in California could also play a role.
While whole-exome sequencing may not be the first screening recommended for newborn screening, it can still be useful in these cases. If a newborn has an MS/MS screen that shows an error, but doctors are unsure what that is, they could use the whole exome sequencing to investigate further. While it may not be the gold standard in newborn screening, whole exome sequencing could still play a role when it comes to metabolic and genetic disease diagnosis.
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