Category Archives: Transhuman News

High-tech blood tests should replace ultrasound and other methods as the primary tools for screening for Down syndrome, argue researchers.

All pregnant womennot just those with high-risk pregnanciesshould be offered a new, DNA-based screening test for Down syndrome, say researchers.

In a study published in the New England Journal of Medicine on Wednesday, DNA-based tests outperformed standard screening methods, which include ultrasound imaging and biochemical test of a mothers blood.

A pregnant womans blood contains bits of DNA from her fetus along with her own. By sequencing this mix of DNA, scientists can determine whether or not her fetus has an abnormal number of chromosomes, such as the extra copy of chromosome 21 that causes Down syndrome. Doctors are already using this finding to screen women who are at high-risk for having pregnancies with this kind of complication (say because they are over the age of 35, see Medical Society Approval for Non-Invasive Prenatal Testing). The new method is safer than traditional tests for counting fetal chromosomes in high-risk pregnancies. Traditionally, that had required amniocentesis or other invasive methods of gathering fetal chromosomes, which carry a small risk of miscarriage or damage to the fetus (see A Safer Test for Down Syndrome).

Several companies now offer the non-invasive, DNA-based test to doctors with high-risk patients, including MIT Technology Reviews Smartest Company of 2014, Illumina (see A Brave New World of Prenatal DNA Sequencing).

But so far, these tests are not used to screen the broader population of pregnant women. Thats still done with ultrasound imaging or biochemical tests that arent very good at actually predicting whether a baby has Down syndrome. When such screening tests flag a pregnancy as having Down syndrome, theres only a four percent chance the fetus actually does have the chromosome abnormality, says Diana Bianchi, executive director of the Mother Infant Research Institute at Tufts Medical Center. Confirming the result is usually done with the invasive testing methods.

Now, in the NEJM study, Bianchi and collaborators at Illumina (which funded the work) report that the blood-based DNA test can detect Down syndrome in any kind of pregnancy, not just high risk. Bianchi says that was not obvious to the field, as some people suspected that the biology of high-risk pregnancies may have led to more fetal DNA in a mothers blood than in low-risk pregnancies.

Compared to the biochemical and ultrasound screening methods, the DNA test did a better job at correctly predicting chromosome problems in fetuses in the general population: a positive screening result for Down syndrome was correct 46% of the time.

For now, if women want the DNA-based tests, they will have to pay for it themselves as insurers dont yet cover it for low-risk pregnancies. The test have list prices range from $1,200 to $2,700 says Richard Rava, chief scientific officer of Verinata, the Illumina division responsible for the prenatal test.

Those prices are significantly higher than they few hundreds of dollars that the biochemical and ultrasound tests each cost. However, given that those tests often incorrectly flag a pregnancy as having Down syndrome, theres the potential for cost savings for insurers. Fewer false positives would mean fewer unnecessary and risky amniocentesis procedures that are required to follow up the screening tests.

Continued here:
Prenatal DNA Tests Should be New Standard, Study Suggests

SAN ANGELO, Texas DNA testimony continued with prosecutors explaining key pieces of evidence, but it did not link the murder weapon to James Winchester.

Winchester, 46, is accused of killing Burton in March 2008 at her house in the 3300 block of Cornell Avenue. Her daughter Erika Heffner found her March 22, 2008, after not being able to reach her for several days.

Burton appeared to be beaten to death with a sledgehammer. Heffner found her mother on the couch with a blanket tucked in over her.

Negin Kuhlmann and Brandi Mohler, who worked as forensic scientists at the Texas Department of Public Safety crime lab in Austin, were the only state witnesses called to testify Thursday morning.

The two tested pieces of evidence in the case, including a gray sweatshirt found with the hammer, Winchesters jersey and a washcloth he reportedly used to wash with early Tuesday morning at a friends apartment on San Antonio Street.

No DNA matches from either Winchester or Dwayne Chadwick, an original suspect in the case, were found on the items, Mohler said. She concluded the blood from the hammer handle was a match for Burtons DNA. She determined that Burton was a source of the major component of DNA from swabs taken in the apartment bathroom sink.

Earlier this year 119th District Judge Woodward sided with defense on a motion to suppress DNA findings in the case.

A probable cause affidavit filed in March 2012 claimed that, according to a Sorenson forensics case report Winchester was the major source of DNA extracted from the hammer handle.

Denise Anderson, forensic supervisor for private lab Sorenson Forensics, was qualified as an expert, but the court said she deviated from accepted scientific protocols, according to the judges order.

It stated the evidence did not prove that: A major DNA profile could be identified from the sample in question, the defendants known DNA matches the profile from the sample, or that reliable tests, or conclusions, can be drawn from a sample of DNA that is only 0.01 nanograms of material.

Read more:
DNA testimony continues in Winchester trial

PUBLIC RELEASE DATE:

26-Feb-2014

Contact: Jeremy Lechan jlechan@tuftsmedicalcenter.org 617-636-0104 Tufts Medical Center

BOSTON (Feb. 27) A study in this week's New England Journal of Medicine potentially has significant implications for prenatal testing for major fetal chromosome abnormalities. The study found that in a head-to-head comparison of noninvasive prenatal testing using cell free DNA (cfDNA) to standard screening methods, cfDNA testing (verifi prenatal test, Illumina, Inc.) significantly reduced the rate of false positive results and had significantly higher positive predictive values for the detection of fetal trisomies 21 and 18.

A team of scientists, led by Diana W. Bianchi, MD, Executive Director of the Mother Infant Research Institute at Floating Hospital for Children at Tufts Medical Center, reports the results of their clinical trial using non-invasive cell-free DNA prenatal testing in a general obstetrical population of pregnant women, in an article entitled "DNA sequencing versus standard prenatal aneuploidy screening."

The multi-center, blinded study analyzed samples from 1,914 pregnant women, and found that noninvasive cfDNA testing had a ten-fold improvement in the positive predictive value for trisomy 21, commonly known as Down syndrome, compared to standard prenatal aneuploidy screening methods (aneuploidy is a term for one or more extra or missing chromosomes). Importantly, the cfDNA test performed consistently well in a general population of pregnant women, regardless of their risk for fetal chromosomal abnormalities. Previous studies have shown that the tests were more accurate for women who had higher risks for fetal chromosomal abnormalities, but this was the first time that the cfDNA tests were compared in a general obstetrical population to the variety of blood and ultrasound tests that comprise the current standard of care in the United States.

"We found that the major advantage of noninvasive prenatal DNA testing was the significant reduction of the false positive rate," said Bianchi. "Prenatal testing using cell-free DNA as a primary screen could eliminate the need for many of the invasive diagnostic procedures (such as amniocentesis) that are performed to confirm a positive screen."

Prenatal screening for fetal aneuploidy is recommended by the American College of Obstetricians and Gynecologists as part of routine prenatal care. Researchers compared current standard noninvasive aneuploidy testing techniques - serum biochemical assays and nuchal translucency measurements using ultrasound - with a noninvasive, cell-free DNA test. Serum biochemical assays identify biomarkers for chromosomal abnormalities while nuchal translucency measurements use ultrasound examinations to measure the thickness of a space at the back of the baby's neck. With Down syndrome, more fluid is present, making the space appear thicker. Cell-free DNA testing works by mapping and counting DNA fragments in a mother's blood sample and comparing the measurements to normal reference samples. The cell-free DNA is obtained through a simple blood draw from the mother after 10 weeks of pregnancy.

The study's endpoint was a comparison of false positive rates for trisomies 21 and 18 between the two methods. The false positive rate for combined trisomies 18 and 21 among those undergoing DNA testing was 0.45 percent while the rate for standard testing was 4.2 percent, a statistically significant difference.

Another comparison was made for positive predictive value of test results: DNA results for trisomy 21 had a predictive value of 45.5 percent compared to 4.2 percent in standard testing; DNA results for trisomy 18 had a predictive value of 40.8 percent compared to 8 percent for standard testing, a significant improvement.

Original post:
DNA test better than standard screens in identifying fetal chromosome abnormalities