"Sequenom could also face heightened skepticism because of its past problems. The company was preparing to introduce another prenatal Down syndrome test in 2009 when it abruptly announced that the data it had promoted to investors could no longer be trusted.It turned out that a top research official had known which samples were positive and negative and had told subordinates to adjust the parameters of the test to improve its accuracy.Five executives, including the chief executive and the research official, were fired. The research official, Elizabeth A. Dragon, pleaded guilty to conspiracy to commit securities fraud. (She died this February, before sentencing.)Sequenom’s stock, which had been over $25 early in 2009, collapsed after the scandal. On Monday it rose 24 cents to close at $5.56.
The Sequenom test correctly identified 209 of the 212 Down syndrome samples, a rate of 98.6 percent. It incorrectly characterized three of 1,471 negative samples as showing Down syndrome. The test could not determine any answer for 13 pregnancies, or about 0.8 percent of cases.
The test counts small fragments of DNA in the mother’s blood. While most of this DNA is from the mother, some is from the fetus. Sequenom uses high-speed gene sequencers to determine the sequence of millions of the fragments. Using knowledge of the human genome, it determines which chromosome each fragment comes from. If the fetus has three copies of chromosome 21, there will be more than the expected number of fragments coming from chromosome 21.
One of the first papers on this approach was published in 2008 by Stephen Quake, a professor of bioengineering and applied physics at Stanford. Verinata has the rights to his discoveries, setting up a potential patent battle with Sequenom.
Professor Quake said that by increasing the number of fragments counted, it would be possible to prenatally diagnose abnormalities that do not involve entire extra chromosomes, even single mutations that cause diseases likecystic fibrosis."