Noninvasive test may cut down on the need for amniocentesis and chorionic villus sampling, both associated with higher risk of miscarriage.

Ravgen scientists say they have perfected the ability to detect fetal DNA from an easily obtained maternal blood sample. They used genetic markers on fetal DNA recovered from maternal blood as the basis for a noninvasive prenatal test. The research relied on SNPs to determine potential chromosomal abnormalities in the fetuses. 

In the current study, 60 blood samples were collected from pregnant patients, with an average age of 34, and the biological fathers. Ravgen scientists used 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 both parents and was used to identify genetic variants unique to each parent. It was then possible to distinguish the fetal variants from the maternal DNA in the maternal plasma.  

Ravgen reports that the results of the study, published in an on-line version of The Lancet, showed that the 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%.

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, Ravgen scientists say that they were correct in two of the three trisomy 21 cases and 56 of the 57 normal cases; one sample was a false negative and one sample a false positive.

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