New test of newborns' DNA speeds diagnosis
10/04/2012 12:00 AM
10/03/2012 11:00 PM
From the day she was born, the baby girl had seizure after seizure as doctors at Children's Mercy Hospital in Kansas City, Mo., frantically tried to keep her alive. Weeks passed and every medication failed. Finally, her family decided to let their baby go, and the medical devices were withdrawn. She was 5 weeks old.
Her doctors suspected a genetic disorder, and as it happened, the hospital had just begun a study of a new technique for quickly analyzing the DNA of newborns, zeroing in on mutations that can cause disease.
This new method, published Wednesday in the magazine Science Translational Medicine, is a proof of concept – a demonstration in four babies that it is possible to quickly scan a baby's entire DNA and pinpoint a disease-causing mutation in a couple of days instead of the more typical weeks or months.
The study's investigators said the test could be one of the first practical fruits of the revolution in sequencing an individual's entire DNA. The hospital found the results so promising that by year's end, it plans to begin routine gene-mapping in its neonatal intensive care unit – and may offer testing for babies elsewhere, too – while further studies continue, Dr. Stephen Kingsmore, director of the pediatric genome center at Children's Mercy, told the Associated Press.
"For the first time, we can actually deliver genome information in time to make a difference," he said.
For the baby with seizures, her doctors provided a sample of her blood. The analysis took only 50 hours and provided an answer: The baby had a mortal gene mutation so rare that it had only been reported once before.
If only the test could have been done within days of the baby's birth, said Dr. Joshua E. Petrikin, one of the baby's doctors.
"There was no treatment, there was not anything that could have changed the outcome," Petrikin said "But we could have more appropriately counseled the family and bypassed what had to have been intense suffering." The baby, he explained, was heavily sedated, medicated and intubated for her entire brief life.
The idea behind the test is to take advantage of what is known about disease symptoms to narrow the search for genetic aberrations. And that, said Dr. Joe Gray, an expert in genome analysis at Oregon Health and Science University, "is a good step in the right direction."
"It's a big genome," said Gray, who was not involved with the study. "How do you know what part of it to search?" While more research needs to be done before the test is ready for widespread use, he applauded the effort. "If people don't push the envelope like this, then we won't get there," Gray said.
About 1 in 20 babies in newborn intensive care units has a genetic disease and all too often, no one can figure out what it is. Scientists identified the faulty genes for about 3,500 of 7,500 known genetic diseases, said the paper's authors, adding that about 500 have treatments.
To test their method, the investigators tried it with two babies whose disease had been diagnosed only through an autopsy. They quickly found the genetic causes. Then they tried the method on four babies who were seriously ill with suspected genetic diseases, including the baby with seizures. They quickly found the mutated gene in three of the four.
The investigators also sequenced the DNA of an older brother of one of the babies who had the same genetic disorder – his organs were reversed. This caused a heart defect, corrected by surgery.
The parents had been told the child had a condition that would not happen again. Then their second baby had the same problem. The researchers found a new genetic defect, never seen before, that they suspect was the cause. They contacted doctors and discovered more than 100 other children with the same unexplained defect.
Now the investigators are checking to see if some have the mutation, which would indicate it caused the problem.
The method is expensive, costing about $13,500. It is not yet covered by insurance. But Kingsmore expects to show it is cost effective and hopes insurers will pay for it.
Kingsmore said the biggest surprise for him was that the families greatly valued having a diagnosis. When a baby has a mysterious disease, he said, the family often embarks on a terrifying diagnostic odyssey.
"Providing a definitive diagnosis somehow brings closure," Kingsmore said. "It is something they can name."
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