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

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

STUDY SUPPORTS LP-PLA2 AS MEASURED BY DIADEXUS PLAC® TEST AS AN INDEPENDENT RISK PREDICTOR OF CORONARY EVENTS AND STROKES

Publication in European Heart Journal Demonstrates Elevated Lp-PLA2 levels are associated with a Higher Incidence of Major Adverse Events Independent of Traditional Risk Factors and CRP

South San Francisco, CA - January 11, 2005 - diaDexus announced today that data from a study supporting the measurement of lipoprotein-associated phospholipase A2 (Lp-PLA2) as an aid in identifying individuals at risk for major adverse events, including stroke and heart attack, was published in this month's issue of the European Heart Journal. The trial evaluated the association of Lp-PLA2 levels with traditional risk factors, angiographic coronary artery disease (CAD), and major adverse events over a four year follow-up period.

Vascular disease, including CAD and stroke, is the leading cause of death in the United States. Nearly half of all coronary events occur in individuals who do not have high cholesterol. Further, elevated levels of cholesterol have not proven to be a reliable risk factor for stroke. Coronary angiography is very effective in detecting stenosis, or the narrowing of the coronary arteries; however it may not detect all high risk vascular conditions. A growing body of evidence suggests that inflammation plays a key role in the formation of less obtrusive plaques, which are often missed with angiography but may be highly prone to rupture and can lead to an acute event. Therefore, novel inflammatory risk factors like Lp-PLA2, may help assess risk in patients without angiographic evidence of CAD and traditional risk factors.

"Our study demonstrates that in patients undergoing clinically indicated angiography, elevated Lp-PLA2 levels were associated with a higher incidence of major adverse events during follow-up, independent of traditional risk factors and CRP," said Emmanouil S. Brilakis, M.D. M.Sc., Assistant Professor of Medicine, The University of Texas Southwestern Medical Center at Dallas. "Lp-PLA2 had a significantly stronger association with major adverse events than with angiographic CAD, which further supports the role of inflammation in the formation of vulnerable or unstable plaque, a condition not typically detected by angiography."

Study Details & Results
Using the diaDexus PLAC® test the research team measured Lp-PLA2 levels in 504 patients undergoing clinically indicated coronary angiography. The patients were aged 26-76 years and 38% were women. While Lp-PLA2 levels were higher in individuals with more angiographic evidence of CAD, in a model adjusted for traditional CAD risk factors there was no significant association between Lp-PLA2 levels and angiographic disease. During a median follow-up of 4.0 years, 72 major adverse events occurred in 61 of 466 patients available for follow-up. The risk of an event increased by 30% (95% CI 1.06-1.59) per standard deviation increase in Lp-PLA2, independent of traditional risk factors and CRP.

"The results from this study complement the observations from previously published reports such as the MONICA, ARIC and WOSCOPS studies, and reinforce the growing body of evidence supporting Lp-PLA2 as a predictor of acute vascular events in various populations," said Robert Wolfert, Ph.D. and vice president of Diagnostics at diaDexus. "These results further validate clinical use of the PLAC test as an aid in identifying individuals who may be at high-risk due to unstable plaque that can benefit from aggressive risk reduction strategies, such as statins and aspirin."

This study was supported by a grant from diaDexus, Inc.

The PLAC test is currently available through laboratories nationwide, including Quest Diagnostics Incorporated, Mayo Medical Laboratories and ARUP Laboratories.

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.