Contacts:

Patrick Plewman diaDexus, Inc. (650) 246-6400

Carolyn Bumgardner Wang WeissComm Partners (415) 362-5018 x123 carolyn@weisscommpartners.com

DIADEXUS SUBMITS 510 (K) PREMARKET NOTIFICATION TO FDA FOR PLAC® TEST FOR STROKE RISK ASSESSMENT

South San Francisco, CA - March 2, 2005 - diaDexus, Inc. today announced submission of a 510(k) Premarket Notification to the U.S. Food and Drug Administration seeking marketing clearance for the PLAC® test as an in vitro diagnostic product to help predict the risk for ischemic stroke. If cleared for marketing, the PLAC® test would be the first blood test with an indication for use in assessing stroke risk. The PLAC® test was originally cleared by the FDA as an aid in predicting an individual's risk for coronary heart disease (CHD) in July 2003, and is currently available through laboratories nationwide, including Quest Diagnostics Incorporated, Mayo Medical Laboratories and ARUP Laboratories.

The PLAC® test is a simple blood test that measures an enzyme in the blood called lipoprotein-associated phospholipase A2 (LP-PLA2 ). Large population studies demonstrate elevated LP-PLA2 is associated with an increased risk of ischemic stroke. An analysis by investigators from the ongoing Atherosclerosis Risk in Communities (ARIC) study presented at the American Heart Association's Scientific Sessions 2004 found that individuals with the highest levels of LP-PLA2 had a statistically significant doubling of risk of ischemic stroke compared with individuals with the lowest levels of the enzyme. This association was independent of traditional risk factors for stroke.

"Currently, there are no U.S. guidelines pertaining specifically to the primary prevention of stroke," said Patrick Plewman, chief executive officer of diaDexus. "There is a clear need for more specific tests to accurately identify those at risk of stroke, so that preventative measures, like lifestyle modification or therapeutic intervention, can be taken. We believe the PLAC® test is an important tool that will help to identify patients at risk for stroke."

According to the American Heart Association, stroke is the third leading cause of death in the United States, and a leading cause of severe, long-term disability. About 700,000 Americans will suffer from a stroke this year and 500,000 of those will be first attacks. Ischemic strokes make up 88% of all strokes. Risk factors for stroke include high blood pressure, smoking, diabetes or other heart disease, and obesity, as well as heredity and race. Warning signs of stroke include: sudden numbness or weakness of the face, arm or leg, especially on one side of the body; sudden confusion, trouble speaking or understanding; sudden trouble seeing in one or both eyes; sudden trouble walking, dizziness, loss of balance or coordination; or a sudden, severe headache with no known cause.

About diaDexus
diaDexus, Inc., a privately held biotechnology company based in South San Francisco, California, is focused on the discovery, development and commercialization of novel, patent-protected diagnostic and therapeutic products with high clinical value. The PLAC® test, developed by diaDexus, Inc., is a blood test cleared by the U.S. Food and Drug Administration to aid in the prediction of an individual's risk for a coronary event, in conjunction with clinical evaluation and patient risk assessment. For more information about the PLAC® test visit www.plactest.com. More information about the company may be found at www.diaDexus.com.