Blood test detects genetic disorders in early pregnancy

By Eytan Holon

Researchers at Tel Aviv University have developed a new blood test to detect genetic disorders in fetuses as early as 11 weeks into pregnancy.

The simple blood test enables doctors to diagnose genetic disorders caused by minuscule impairments in the fetal genome by sequencing small amounts of DNA in the mother’s and the father’s blood.

A computer algorithm processes the sequencing results to produce a “map” of the fetal genome, identifying countless mutations with at least 99% accuracy, depending on the mutation type.

The research, led by Prof. Noam Shomron of the university’s Sackler School of Medicine, was published recently in the Genome Research journal.

“Non-invasive prenatal tests are already available for chromosome disorders such as Down syndrome,” said Prof. Shomron.

“Our new procedure is based on fetal DNA fragments that circulate freely in maternal blood and bears only a minimal risk for the mother and fetus compared with such invasive techniques as the amniotic fluid test. We will now be able to identify numerous mutations and diseases in a safe and simple procedure available at the doctor’s office.”

While the genetic mechanism behind Down syndrome affects a large portion of the fetal genome, and is therefore easier to detect, researchers say the improved algorithm will enable physicians to detect other diseases caused by smaller parts of the genome.

“This is like looking at a map of the world and noticing not only that a continent is missing, but also that a single house is missing,” said Prof. Shomron.

Together with graduate student Tom Rabinowitz, researchers from Tel Aviv University and Haifa’s Technion-Israel Institute of Technology, Prof. Shomron partnered with the Rabin Medical Center to test blood samples from three families in the 11th week of gestation.

Researchers extracted maternal and paternal DNA from white blood cells and fetal DNA from a placental cell sample. They also extracted cell-free fetal DNA from the maternal blood.

“We sequenced all these DNA samples and created a computer algorithm that utilizes the parental DNA as well as the cell-free fetal DNA to reconstruct the fetal genome and predict mutations,” said Prof. Shomron.

“We compared our predictions to the true fetal DNA originating from the placenta. Our model is the first to predict small inherited insertions and deletions. The method described can serve as a general framework for non-invasive prenatal diagnoses.”

Researchers are currently working on further improving the accuracy of the algorithm and enabling the detection of additional mutations.

“The practical applications are endless: a single blood test that would detect a wide range of genetic diseases, such as Tay-Sachs disease, cystic fibrosis and many others.”