A new study has shown that prenatal DNA tests accurately detect fetal disorders. The tests are typically used to detect conditions such as Down’s syndrome, and have proven more accurate that previous methods in a trial published in the New England Journal of Medicine.
The new results are important as many people in the US and beyond suffer from what is termed a “rare” disease. Almost 30 million Americans suffer from what has been classed as a rare disease, and they are nearly all genetically based health issues. Prenatal screening programs such as this, will likely help in understanding the severity of the illness before a pregnancy comes to term.
In the current study the testing is focused on finding diseases that involve the inclusion of an extra chromosome, such as Down’s syndrome, in low risk women. This is now believed to be the best non-invasive test currently available, compared to previous types of blood analysis or even ultrasound testing. The study was led by Dr. Diana Bianchi, a Boston-based physician and executive director of the Mother Infant Research Institute at Tufts Medical Center. The study also found that the test produced less false positives than other methods. The tests are currently offered by Illumina Inc., and they were also the source of funding for the study, but their case has new been backed up by several prestigious medical voices.
The basis of the test is that significant amounts of fetal DNA are present in the mother’s blood stream during pregnancy. The DNA sections originate in the placenta, but can be easily recovered from a blood test carried out on the mother. The samples are then fed into a gene sequencing machine, that produces thousands of copies of the DNA fragments, and analysed. If too much of certain pieces of DNA are found, a warning is given, and that is how the prenatal DNA test accurately detects fetal disorders.
The study evaluated the test in over 1,900 pregnancies, and is now slated to be an early warning system that will lead to more comprehensive tests where warning signs are detected. All women are recommended to be tested by their doctor for conditions such as Down’s syndrome, but previous tests that relied on the balance of certain chemicals in the blood led to a number of false positive results, that then triggered invasive testing unnecessarily. In fact, such test generated 69 false reports for every accurate prediction, with the new test the results have an accuracy of 1 in 2.
Some observers have also raised the concern that the test can be quite expensive, and so unavailable to many, and is still some way from a perfect test. Others have also raised reservations about the results of these test triggering abortions. Even Down’s syndrome support groups point to many abilities of people who suffer from the syndrome, and resist the blanket suggestion that the removal of all children with Down’s syndrome would be a good thing.
However, it is expected that this procedure will become popular as a prenatal DNA test that accurately detects fetal disorders.
By Andrew Willig