Sequenom developed a noninvasive prenatal diagnostic test to assess the risk of Down syndrome or other chromosomal abnormalities in fetuses. The test analyzes DNA from the fetus that is found in the mother's blood. Prior to this test, women had to undergo invasive tests that carried a slight risk of miscarriage. The PTO awarded Sequenom a patent on the test, but other diagnostic testing companies sued to invalidate the patent. Is Sequenom's patent valid?