THE Pap smear test, widely used to screen for cervical cancer, is being modified to create a safe prenatal test for genetic disorders such as Down鈥檚 syndrome. If it turns out to be reliable and affordable, it could lead to a massive increase in prenatal screening.
With existing invasive screening methods, there is a small risk of triggering miscarriages, so usually only those women at high risk of having a child with a genetic disorder opt for tests. But most children with genetic disorders are born to women who were considered to be at low risk.
A safe test, however, could be offered to all pregnant women, and smear tests have a good track record. 鈥淧ap smears during pregnancy have been safely performed for decades,鈥� says Ian Findlay of the Australian Genome Research Facility in Brisbane, whose team is developing the test. He also thinks testing could be done far earlier in pregnancy than at present. In remote areas samples could even be mailed to labs for analysis.
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It has been known for a while that stray cells from the fetus end up on the cervix. The difficult part is finding them. Findlay claims to have developed ways of identifying and isolating fetal cells based on their surface characteristics. Single cells can then be tested to confirm that they are from the fetus, and further tests are done to spot a range of genetic abnormalities.
Findlay will not reveal any details of the separation technique before a patent is granted. But his team is already starting to do the work needed to prove the test is reliable, by analysing smears from 600 pregnant women. The results will be compared with conventional tests carried out on the babies after birth to see how good the test is at spotting defects.
鈥淚f it makes it to the clinic it will be excellent,鈥� says Bob Williamson of the Murdoch Childrens Research Institute in Melbourne. 鈥淒octors have wanted a non-invasive test to see if a pregnancy is affected by an inherited or genetic disease for a long time.鈥�
