Sequencing-based test effectively detects many fetal genetic defects

By Helen Albert, Senior medwireNews Reporter

medwireNews: Researchers have developed a new screening test that allows detection of fetal abnormalities in maternal blood by deep sequencing cell-free (cf) DNA extracted from plasma.

They hope the test will eventually provide a safe and effective alternative for pregnant women who are reluctant to undergo current testing, due to the associated miscarriage risks.

"Our study is the first to show that almost all the information that is available from an invasive procedure is also available noninvasively from a simple maternal blood draw," says study author Richard Rava (Verinata Health, California, USA) in a press statement.

Rava and co-authors took samples of cfDNA from the blood of 11 pregnant women who were carrying fetuses with a variety of chromosomal impairments, including subchromosomal duplications and deletions, translocations, mosaicism, and trisomy 20, as diagnosed from standard karyotypes obtained using either chorionic villus sampling or amniocentesis.

As reported in The American Journal of Human Genetics, the researchers used a technique known as massively parallel sequencing (MPS) to analyse the cfDNA samples to assess fetal subchromosome abnormalities from the fetal fraction of cfDNA present in the maternal serum (typically 10-15%).

Rava and team found that all the microdeletions, duplications, translocations, and the trisomy 20 case were detected by MPS (n=7). One of the cases detected was a very small microdeletion of 300 kb, and MPS also managed to provide more detailed information than that provided using karyotype analysis alone for two translocation cases, including information on the chromosomal origin of the additional genetic material and the translocation breakpoints.

However, MPS did not detect the four cases of mosaicism diagnosed via metaphase karyotype analysis.

"Such a noninvasive test could have clinical utility in the near future, particularly for women who either have a medical contraindication or lack access to an invasive procedure," commented Rava in a press statement.

"This work suggests an exciting future path toward routine noninvasive detection of abnormalities in the entire fetal genome," he said.

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