On Oct. 6, 2008, Stanford researchers developed a test that reduced the risks in testing for chromosomal disorders such as Down syndrome. The new method, developed by scientists at Stanford University, the Howard Hughes Medical Institute and Lucile Packard Children’s Hospital, requires only a maternal blood sample to spot chromosomal disorders such as Down syndrome.

“Non-invasive testing will be much safer than current approaches,” said Stephen Quake, PhD, professor of bioengineering and the study’s senior author. The new technique, which takes advantage of fragments of fetal DNA in the woman’s blood, published online the week of Oct. 6 in the Proceedings of the National Academy of Sciences. Safety may not be the only gain.

Quake hopes the test will spot genetic problems much earlier in gestation than the other methods.
The new method scans for fetal aneuploidy, an abnormality in the number of fetal chromosomes. Humans typically inherit 46 chromosomes, half from each parent. Errors in chromosome number cause serious problems in physical and mental development. Down syndrome, for example, arises from an extra copy of chromosome 21.

The Stanford/Packard team developed a way to count chromosomes using bits of fetal DNA in a pregnant woman’s blood. Other scientists had struggled to tease these tiny genetic clues apart from a mom’s DNA, said Quake, who is also an HHMI investigator. His team made an ingenious simplification: their new method has no need to distinguish between maternal and fetal DNA.

First, using samples from 12 women with aneuploid pregnancies and six with normal pregnancies, the researchers separated maternal blood into cells and plasma. They discarded the blood cells, focusing on the liquid plasma’s DNA fragments, which come from both the mom and the fetus. They counted the number of DNA fragments and used DNA sequencing to read each one.

The next step, the scientists say, is to repeat their study in a larger number of women. If their technique holds up in further research, they expect that it would be simple and inexpensive to use in clinical settings, especially as other forms of genetic testing also become popular. Quake expects it will take the new test two to three years to reach the clinic, assuming that the larger trial is successful.

Stanford is filing a patent application for the new technique, and Quake consults for two potential licensees.