Picking the Best Embryo from the Bunch

Continued from page 1

By Emily Singer

Tuesday, January 09, 2007

William Kearns, director of the Shady Grove Center for Preimplantation Genetic Diagnosis, a commercial genetic-testing center in Washington, D.C., and his colleagues have developed a more accurate amplification technique. Kearns is now developing a specialized microarray that will detect not only chromosomal abnormalities, but also several other genetic characteristics, including small duplications or deletions of DNA and genetic variations linked to single-gene disorders, which are currently detected with another method. "I think being able to look at all these things will increase chances of having a successful pregnancy," says Kearns. "Eventually, I think everyone undergoing IVF will do it." So far, Kearns has tested the technology on genetically abnormal embryos donated for research. He expects the test to be clinically available in three to six months.

This type of methodology should also improve error rates, says Santiago Munnes, director of Reprogenetics, a genetic-testing laboratory in Livingstone, NY. Munnes's team is developing a similar set of new screening tools. Because laboratories have only a single cell to work with, they can't repeat tests for accuracy, and error rates vary widely, depending on how the cell is prepared and who is running the test. In addition, the current screening method analyzes only one spot on the chromosome, while microarray tests could analyze four to five spots per chromosome.

It's not yet clear how much such tests will cost. Munnes's team plans to develop a relatively simple test designed to detect 100 to 150 genetic markers, and he hopes it will be in the same price range--about $2,000--as the current test. Kearns is developing a more extensive test, examining 500,000 markers per embryo, which is likely to be more expensive. It will also collect much more genetic information, including information that won't be immediately useful but may aid in predicting complex diseases as the child grows older and scientists better understand the genetics of these illnesses.

The new tools will need extensive testing before doctors know how helpful they are and in what group of patients they may be most successful. (Unlike drugs, there is little regulation outlining the types of clinical testing necessary before a product can be sold in the clinic.) "I am very hopeful that the technology is going to improve to the point where it will be very effective and helpful in improving pregnancy rates in IVF patients," says Adamson. "But we still have more research to do."