San Francisco, CA, May 7, 2007 -- XDx, a molecular diagnostics company, today announced its AlloMap molecular expression test will be the subject of presentations and discussions at the American Transplant Congress 2007 held here, May 5 to 9.

The test, currently used to detect the absence of heart transplant rejection instead of routine invasive heart muscle biopsies, has now been shown to correlate with oxygen saturation levels, cardiac filling pressures, and the electrical properties of the transplanted heart. Also, data from the Lung Allograft Rejection Gene expression Observation (LARGO) study presented at the ATC sessions demonstrate that a non-invasive blood test can detect cytomegalovirus-induced immune responses in lung transplant patients.

"These data continue to validate the outcomes of the Cardio Allograft Gene Expression Observational (CARGO) and LARGO studies and demonstrate how non-invasive molecular expression testing can be used clinically," said Mario C. Deng, M.D., director of Cardiac Transplantation Research, Columbia University Medical Center/New York-Presbyterian Hospital, and co-principal investigator in the Cardiac Allograft Gene Expression Observational (CARGO) study. "For the 21,000 U.S. heart transplant patients undergoing an estimated 40,000 heart muscle biopsies each year, a non-invasive test is a welcome alternative."

In separate studies, recent data from the CARGO study show that the non-invasive AlloMap molecular test may help reduce the use of immunosuppressants without the need for invasive biopsies and can serve to measure heart graft blood flow and blood pressure.