Sequenom ( SQNM) is leaning towards making a big change in the technology that forms the basis for its prenatal genetic screening test for Down syndrome. The San Diego-based genetics testing company is working quickly to perfect and validate a DNA-based screening method for its Down syndrome test in time for a commercial launch this summer, said Sequenom CEO Harry Stylli in an interview Tuesday. This represents a change in strategy for Sequenom, which had previously told investors that the company intended to launch an RNA-based version of the Down syndrome test in the same time frame. "We are maturing both the RNA-based and DNA-based tests simultaneously, but we are close to choosing a launch with the DNA test only," said Stylli. The stakes are high for Sequenom, which is betting its future on widespread adoption of a genetic test for Down syndrome and other infant disorders that it believes will prove to be superior and safer than current screening methods and diagnostic tests like amniocentesis. If that occurs, Sequenom could stake a large claim to a $2 billion-a-year prenatal testing market. Investors were only just beginning to digest data from January fleshing out the accuracy of Sequenom's RNA-based test. Now, the company is essentially shunting all that data aside and telling investors to have equal confidence in a new, less-proven DNA-based test. When word of the company's decision first surfaced during a health care conference last week, Sequenom shares dipped because investors were concerned about the relative paucity of data collected to date confirming the accuracy of the DNA-based Down syndrome test.