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Barbara Sullivan Sullivan & Associates 714/374-6174 bsullivan@sullivanpr.com

DIADEXUS APPOINTS CHARLES PATRICK TO BOARD OF DIRECTORS

South San Francisco, CA - May 3, 2007 - diaDexus, Inc., a privately held biotechnology company and developer of the PLAC® test, today announced the appointment of Charles (Chuck) Patrick to its Board of Directors. Patrick brings nearly 30 years of experience working with and managing high growth diagnostic companies with an emphasis in the areas of sales, marketing, and global distribution.

Since 2000, Patrick has worked as a management consultant helping diagnostic and technology companies develop sales, marketing, and distribution strategies. He also served as President and Chief Executive Officer for CallNexus, Inc. From 1990 to 2000, Patrick was Vice President of Sales and Marketing for Biosite, Inc., and was instrumental in building the company into a leading provider of rapid diagnostics for drugs of abuse and cardiac products for hospitals. He also played a key role in establishing Biosite's international sales and distribution capabilities. Patrick began his career with the diagnostics division of Abbott Laboratories in various sales and marketing management capacities, leading to the position of Worldwide Group Marketing Manager.

"I am extremely pleased to welcome Chuck Patrick to our Board of Directors," said Patrick Plewman, President and Chief Executive Officer of diaDexus. "We look forward to benefiting from Chuck's wealth of experience as we continue to develop the commercial strategy for the PLAC test, our novel cardiovascular assay."

Patrick also is a director of OraSure Technologies, Inc., the market leader in oral fluid diagnostics, and previously was on the Board of Directors for Accumetrics, Inc., a privately held cardiac diagnostic company.

About diaDexus
diaDexus, Inc., based in South San Francisco, is focused on the discovery, development, and commercialization of innovative, patent-protected diagnostic products with high clinical value. The PLAC test is a simple blood test that measures a new risk factor for coronary heart disease and stroke—lipoprotein-associated phospholipase A2 (Lp-PLA2), a cardiovascular-specific inflammatory marker implicated in the formation of vulnerable, rupture-prone plaque. The PLAC test is cleared for marketing by the Food and Drug Administration as an aid in determining risk for coronary heart disease and ischemic stroke associated with atherosclerosis. In addition to the PLAC test, diaDexus is developing a pipeline of novel cancer diagnostic tests. For more information, visit www.plactest.com or www.diaDexus.com.