Semiconductor sequencing allows for a noninvasive way to detect chromosomal abnormalities. (Photo : Wikipedia)
Researchers from China and the U.S. announced on Monday that they can now use a simple blood test called noninvasive prenatal testing (NIPT) to detect more types of chromosomal abnormalities through a new method known as semiconductor sequencing.
The U.S. journal Proceedings of the National Academy of Sciences published a study wherein they identified small chromosomal deletions or duplications, like those that are found in Cri du Chat syndrome and DiGeorge syndrome, using a semiconductor sequencing platform on the blood plasma of the expectant mother.
Currently, identifying these types of chromosomal abnormalities requires invasive procedures to obtain fetal DNA, such as chorionic villus sampling or amniocentesis, which has a small risk of miscarriage or infection.
The recent discovery of fetal DNA found in the blood of pregnant women has led to NIPT being used more to detect certain chromosomal abnormalities by extracting the expectant mother's blood.
As of now, NIPT is only being typically used to detect abnormalities that are caused by larger chromosomal abnormalities, wherein there is too many or too few of a particular chromosome, such as the case in Down syndrome.
"We have found that NIPT can be extended in a way that allows us to zoom in and examine a small segment of a chromosome," said the paper's lead author Kang Zhang in a statement. "And while this study focused on cell-free DNA sequencing in pregnant women, this method could be applied more broadly to other genetic diagnoses, such as analyzing circulating tumor DNA for detection of cancer."
Zhang's team analyzed blood plasma from 1,476 pregnant women who already had fetal structural abnormalities detected via ultrasound. These women were also subjected to the conventional invasive diagnostic procedures.
Researchers compared the results obtained from the ultrasound and the invasive methods with those obtained from semiconductor sequencing.
The new method detected 69 out of 73 abnormalities that are larger than one million base pairs.
Semiconductor sequencing is also seen as a less costly, less invasive alternative.
However, there is still much room for improvement.
Semiconductor sequencing detected 55 false positives, with 35 of them due to maternal chromosomal abnormalities, rather than fetal ones.
The new method will have to include a validation test to screen out maternal abnormalities.
NIPT with semiconductor sequencing is also restricted to the first 12 to 16 weeks of the pregnancy, according to researchers.
