Contacts:

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

Christina Andrian diaDexus, Inc. (650) 246-6476 candrian@diadexus.com

PANEL RECOMMENDS VALUES FOR LP-PLA2 IN THE ASSESSMENT OF CARDIOVASCULAR DISEASE RISK

diaDexus' PLAC® Test Predicts Risk of Heart Disease and Stroke

South San Francisco, CA - August 1, 2006 - diaDexus, Inc., today announced the publication of the first recommendations for a proposed cut point for lipoprotein-associated phospholipase A2 (Lp-PLA2), an enzyme that independently predicts the risk of coronary heart disease and ischemic stroke. The report was published in the Summer 2006, issue of Preventive Cardiology.

The paper proposes that clinical laboratories set >235 ng/mL (the median value of the samples analyzed in this study) as the Lp-PLA2 concentration decision value to be used to decide whether patients should be moved to a higher cardiovascular risk category. This cut point is not proposed as a treatment target, but rather as a level above which patients should be considered at increased risk for cardiovascular disease. Lp-PLA2, a cardiovascular-specific inflammatory biomarker, is measured from a blood sample using the PLAC test, developed by diaDexus. The PLAC test has been cleared for marketing by the U.S. Food and Drug Administration as an aid in predicting risk for coronary heart disease and ischemic stroke associated with atherosclerosis.

The recommendations are based on analysis of data from selected published epidemiological studies, as well as a combined dataset from more than 17,000 freshly drawn patient samples. Participating clinical laboratories included ARUP Laboratories, Berkeley HeartLab, Mayo Medical Laboratories, and Quest Diagnostics, Incorporated.

Richard B. Lanman, M.D., chief medical officer of diaDexus and lead author on the report, said that a growing number of studies have demonstrated an independent association between plasma Lp-PLA2 concentrations and risk of subsequent cardiovascular events. "diaDexus invited a panel of national experts in laboratory medicine and cardiology to assist in establishing a cut point recommendation to help clinicians incorporate this specific marker of unstable plaque into practice," Lanman said. Further studies of potential differences in Lp-PLA2 levels for cardiovascular risk by gender and ethnicity are recommended.

Lp-PLA2 is an enzyme that associates in the blood primarily with low-density lipoprotein (LDL, the "bad" cholesterol). Lp-PLA2 is carried to the walls of coronary arteries by LDL, where the enzyme can activate an inflammatory response, promoting atherosclerosis. As a result, Lp-PLA2 serves as a specific indicator of vascular inflammation. Currently, there are no marketed treatments that directly target Lp-PLA2; however, several compounds are in clinical development.

About diaDexus
diaDexus, Inc., a privately held biotechnology company based in South San Francisco, is focused on the discovery, development, and commercialization of novel, patent-protected diagnostic products with high clinical value. The PLAC® test is a blood test cleared for marketing by the U.S. Food and Drug Administration to aid in the prediction of an individual's risk for coronary heart disease or ischemic stroke, in conjunction with clinical evaluation and patient risk assessment.

For more information, visit www.plactest.com or www.diaDexus.com