LOS ANGELES — Scientists have developed a noninvasive “genetic Pap” test to screen for Down syndrome and other chromosomal abnormalities early in pregnancy.
The test analyzes trophoblast cells shed by the fetus and scraped from the cervix, investigator Moshe D. Fejgin, M.D., reported in an oral presentation at the annual meeting of the Society for Gynecologic Investigation.
Researchers found fetal cells in about 87% of nearly 500 samples from two studies. The test identified two cases of trisomy 21 and one case each of Turner's syndrome and Klinefelter's syndrome in 110 pregnancies, according to Dr. Fejgin of the Meir Medical Center in Kfar Saba, Israel.
Gender predictions were correct in 92% of samples, he said, with accuracy ranging from 89% in samples from women planning to complete their pregnancies and 94% from a group that chose termination. Dr. Fejgin described the test as 100% accurate in determining male gender.
“When you are running 80%–90% accuracy, it can be used as a diagnostic,” Dr. Fejgin said.
He and his coinvestigators concluded that the “genetic Pap” has the potential to replace other noninvasive screening techniques for Down syndrome.
Their announced goal is to find an alternative to invasive procedures such as amniocentesis and chorionic villi sampling, which can be risky as well as costly.
The concept is not entirely new. Scientists have long attempted to isolate fetal cells from maternal blood for this purpose without success, according to Dr. Fejgin.
Fetal cells are shed into the cervix between 5 and 12 weeks of gestation, Dr. Fejgin said, describing the time frame as a window of opportunity for the “genetic Pap.”
After the cells are obtained with a cytobrush, the screening process includes immunohistochemistry and fluorescence in situ hybridization (FISH) analysis for gender and for chromosomal abnormalities.
The investigators have formed a company to commercialize the test, Dr. Fejgin added during an interview.
He said they plan to start clinical trials in Europe and the United States and plan to submit the test to the Food and Drug Administration for approval.