Prenatal genetic tests such as amniocentesis (drawing some amniotic fluid from around a 16-week fetus) always carries a small risk of miscarriage. Now, a partnership between a group of Chinese researchers and a San Diego biotech company may result in a simple no-risk blood test that detects defects caused by single-gene mutations.

Chinese University of Hong Kong scientists report in the Proceedings of the National Academy of Sciences that they devised a technique that locates a fetus's DNA molecules in blood samples taken from its mother. The fetal DNA or genetic material, which tends to be shorter than that of the mom, is duplicated and subjected to a “molecular counting” technique that tallies both mutant and normal genetic material.  The new method overcomes what had been the major obstacle to such testing: distinguishing fetal DNA inherited from mom from mom's own DNA,

The range of single-gene disorders is vast, from cystic fibrosis to sickle-cell anemia  (a disease in which abnormal amounts of iron-rich protein or hemoglobin cause normally round red blood cells to be sickle- or c-shaped and to clump together, blocking blood flow to limbs and organs).  Biotech company Sequenom, which is already developing a blood test for Down’s Syndrome, says it plans to begin work on a commercial test for single-gene disorders.

“If you look at the very rare disorders, you’re into the five to ten- thousand range,” of diseases that might be detected with this test, says Harry Stylli, president and chief executive of the California-based company, which licensed the technology from the university. He notes that, eventually, it may be possible for physicians to order a customized battery of tests based on a patient’s risk profile.

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