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Ravgen Publishes Study In The Lancet Describing A Non-Invasive Test For Prenatal Diagnosis Based On Fetal DNA In Maternal Blood

2/2/2007 10:27:04 AM

COLUMBIA, Md., Feb. 1 /PRNewswire/ -- Ravgen, a privately held company dedicated to revolutionizing diagnosis and treatment of human diseases through innovative new technologies, announced today the publication of a study using genetic markers on fetal DNA recovered from maternal blood as the basis for a non-invasive prenatal test. The study being published in early release online in the medical journal The Lancet, by Dhallan et al, relied on common genetic variants in the human genome called single nucleotide polymorphisms (SNPs) to determine potential chromosomal abnormalities in the fetuses.

According to the National Center for Health Statistics, there has been a steady increase in pregnancies in women over age 35. Since advanced maternal age is a risk factor for genetic abnormalities, prenatal testing will be necessary for more and more women. Also, in a recent bulletin, the American College of Obstetricians and Gynecologists (ACOG) recommended that all women, irrespective of maternal age, be offered genetic screening. Already each year between 150,000 and 200,000 women in the United States receive a positive result from screening tests, and face the decision of whether or not to undergo invasive diagnostic testing. Invasive prenatal tests such as amniocentesis and chorionic villus sampling are performed on pregnant women to determine potential fetal chromosomal abnormalities such as trisomy 21 (Down's syndrome). These tests, while accurate, are associated with increased risk of miscarriage. An accurate, non-invasive, blood test using DNA-based information would be a welcome advance in prenatal testing.

It has long been known that some fetal cells circulate in the maternal blood during pregnancy so research has focused on trying to develop a blood- based prenatal test. However, such tests have remained elusive given the difficulty in separating the small number of fetal cells from the maternal blood. Ravgen scientists have perfected the ability to detect fetal DNA from an easily obtained maternal blood sample. With the availability of human genome sequence data, which provides enhanced understanding of genetic variations such as SNPs, Ravgen scientists are making significant advances toward a DNA-based, non-invasive prenatal test.

In the current study in The Lancet, 60 blood samples were collected from pregnant patients (average age was 34) and the biological fathers from clinical sites in the United States. Using previously reported, proprietary techniques, Ravgen scientists used the chemical formaldehyde, in addition to processing techniques to analyze a higher percentage of fetal DNA from the maternal blood.

DNA was then extracted from white blood cells from the blood samples of both parents and was used to identify genetic variants unique to each parent. Since the fetus has genetic markers contributed by each parent, it was then possible for Ravgen scientists to distinguish the fetal variants from the maternal DNA in the maternal plasma. The DNA assay is quantitative, thus they could determine chromosome copy number and distinguish normal samples from those with trisomy 21.

The results of the study showed that the Ravgen methods enabled the direct detection of fetal DNA in the mixture of maternal and fetal DNA, which is normally present in the maternal bloodstream during pregnancy (the average percentage of fetal DNA identified was 34.0%). Genetic abnormalities can be identified by measuring the number of copies of SNPs on different chromosomes. Of the 60 samples analyzed, Ravgen scientists identified three trisomy 21 samples, and 57 with a normal copy number of chromosomes 13 and 21. By comparing these results to amniocentesis or newborn reports from the clinical sites, it was shown that Ravgen scientists were correct in two of the three trisomy 21 cases and were correct in 56 of the 57 normal cases (one sample was a false negative and one sample a false positive).

"We are encouraged by our results in this study showing that fetal DNA signal can be detected and more importantly fetal chromosomal abnormalities can be identified by using non-invasive, genomic data," said lead author Ravinder Dhallan, M.D., Ph.D., C.E.O. of Ravgen. "We are already working toward the next stages in our research to enable a rapid, reproducible, cost- effective non-invasive prenatal diagnostic since we understand the critical need for such a test."

About Ravgen

Ravgen is a privately held company devoted to solving major clinical problems using new methods to rapidly analyze variations in a genome. This method eclipses background signals, shifting the focus toward genetic markers that are present at the earliest stages of a disease. Ravinder Dhallan, a doctor and researcher, founded Ravgen in September 2000 with the goal of solving major clinical problems. His experiences in biomedical engineering, clinical research and medicine have shaped the research and fueled innovation that can directly benefit patients.


CONTACT: Heather Kowalski, +1-202-294-9206,, for Ravgen

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