Contacts:

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

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

Scientific Sessions Abstract Oral Session #3577 & Poster Session #1477

DATA PRESENTED AT AHA SCIENTIFIC SESSIONS 2004 DEMONSTRATE ELEVATED Lp-PLA2 LEVELS PREDICT CORONARY ARTERY DISEASE

Second Study Highlights Specificity of the PLAC® Test in Measuring Inflammation

New Orleans, LA - Nov. 10, 2004 - diaDexus today announced findings from two studies that were presented at the American Heart Association (AHA) Scientific Sessions held in New Orleans this week. The first study confirms that elevated levels of Lp-PLA2 (lipoprotein-associated phospholipase A2) independently predict stable coronary artery disease (CAD). An additional study found that Lp-PLA2, as measured by the diaDexus PLAC Test, is not commonly elevated in response to systemic inflammation and has only modest biological variability.

In the first study, "Association between Lipoprotein-Associated Phospholipase A2 and Coronary Artery Disease: Focus on its Relationship with Lipoproteins and Markers of Inflammation and Hemostasis," researchers found that individuals with the highest levels of Lp-PLA2 were approximately twice as likely to have CAD as those with the lowest levels.

"The results from our study further support a growing body of evidence that Lp-PLA2 is a novel, independent risk marker for CAD," said Professor Wolfgang Koenig, M.D., Department of Internal Medicine II-Cardiology, University of Ulm Medical Center, Ulm, Germany, and lead investigator of the study. "Since nearly half of all coronary events occur in people who have low to moderate LDL cholesterol levels, there is a pressing need for additional independent risk markers to help determine who is at high risk for coronary disease."

A second study, "Biological Variability and Specificity of Lp-PLA2, a Novel Marker of Cardiovascular Risk," utilized the PLAC Test to measure Lp-PLA2 levels over four weeks in 43 non-fasting healthy adults. Lp-PLA2 was found to display only modest variation, comparable to the measurements of the traditional lipid parameters, while C-reactive protein (CRP) measurements showed significant biovariability over the study period.

The team of diaDexus investigators also evaluated the cardiovascular specificity of Lp-PLA2 compared to three other inflammatory markers in patients with a variety of systemic inflammatory conditions. Among all inflammatory conditions, Lp-PLA2 was elevated in only 10-15% of individuals, while the other inflammatory markers were elevated in as many as 50% of those subjects, indicating that Lp-PLA2 may be a more specific marker of vascular inflammation.

"Several studies have highlighted Lp-PLA2 as an independent risk factor for coronary heart disease," said Bob Wolfert, Ph.D., Vice President of Diagnostics at diaDexus. "Our current research highlights Lp-PLA2 as a specific marker of vascular inflammation that is not commonly elevated in response to systemic inflammation, adding to its clinical value in the detection and monitoring of cardiovascular risk."

Dr. Koenig's study was supported by a grant from diaDexus, Inc.

About Lp-PLA2
Lp-PLA2 (lipoprotein-associated phospholipase A2) is an enzyme that is implicated in the vascular inflammatory pathway that leads to plaque formation and atherosclerosis. Previous hypotheses on the cause of coronary heart disease focused around lipid accumulation within the arterial walls. Increasing evidence now suggests that atherosclerosis is largely an inflammatory disease. The MONICA (MONItoring of trends and determinants in CArdiovascular disease) study, published in the October 2004 issue of Circulation, was the third study published in a peer-reviewed journal to show a statistically significant relationship between elevated Lp-PLA2 and the risk of a coronary event. Among individuals in the MONICA population, each standard deviation increase in Lp-PLA2 levels resulted in a 37% increase in the risk of a coronary event.

About diaDexus
diaDexus, 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, 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. The PLAC test is currently available through laboratories nationwide. For more information about the PLAC test visit www.plactest.com. More information about the company may be found at www.diaDexus.com.