Has one of the most in-demand but controversial genetic tests finally been mastered? That鈥檚 the claim of the (DDC) in Fairfield, Ohio, which this week launched that can be run on a sample of a pregnant woman鈥檚 blood.
The new test comes with a hefty price tag: $1625. But if it performs as advertised, it would free women who want to verify who is the father of their unborn child from the need to undergo invasive procedures to sample fetal cells that carry a small risk of triggering a miscarriage.
DDC鈥檚 announcement is causing a stir because it is one of the biggest providers of paternity tests in the US, and is a member of the industry鈥檚 leading accreditation scheme, run by the (AABB). DDC says that the results of experiments validating the new test are being prepared for submission to a peer-reviewed journal, and have been sent to the AABB for certification.
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The technology behind the test was developed by another company, of Redwood City in California. The method probes single-letter variants in the genetic code known as single nucleotide polymorphisms, or SNPs. The new tests It uses 鈥淒NA chips鈥� to record 317,000 SNPs across the entire genome.
The key problem in running a paternity test on a pregnant woman鈥檚 blood is working out which DNA comes from the fetus, and which from the woman. The new test establishes the mother鈥檚 SNP profile by separating out blood cells, the vast majority of which will come from the woman, from the clear plasma. Algorithms then 鈥渟ubtract鈥� the maternal profile from that recorded from DNA in the blood plasma 鈥� around 10 per cent of which can come from fetal cells that have broken down 鈥� to produce a fetal profile for comparison against DNA samples from the possible fathers..
, DDC鈥檚 chief science officer, claims that the method is extremely reliable when run on blood from women who are at least 12 weeks pregnant. Tests using the profiles of 1000 men who later proved not to be the fathers on the basis of conventional paternity tests produced no false positive results, he says. Baird adds that tests on around 100 men who were the actual fathers turned up no false negatives. In less than 1 per cent of cases, says Baird, it has not been possible to produce a definitive answer.
鈥淧aternity testing does change a person鈥檚 life,鈥� says Baird. 鈥淵ou don鈥檛 want to give the wrong answer.鈥�
Other geneticists say that the method should work in theory, given the large number of SNPs being analysed. 鈥淥f course we have to see the data,鈥� says of the University of North Texas Health Science Center in Fort Worth, and formerly the FBI鈥檚 leading DNA testing specialist. 鈥淏ut in general, it seems a more viable approach.鈥�
鈥淚f you鈥檙e using that many SNPs, that鈥檚 probably a pretty reasonable way of doing it,鈥� agrees of Barts and the London School of Medicine and Dentistry.
