Contacts:	Sharon Tetlow diaDexus, Inc. (650) 246-6400		Ronald L. Weiss, M.D., M.B.A. ARUP Laboratories (801) 584-5188
			Jim Weiss Weisscom (415) 609-3680

DIADEXUS PARTNERS WITH ARUP LABORATORIES TO MAKE NOVEL PLAC® TEST AVAILABLE TO MEASURE INCREASED RISK FOR CORONARY HEART DISEASE

South San Francisco, CA - July 22, 2004 - diaDexus, Inc., a privately held biotechnology company, today announced that ARUP Laboratories, a national reference laboratory, (Salt Lake City, UT) will make the FDA-cleared PLAC® test available for the quantitative measurement of lipoprotein-associated phospholipase A2 (Lp-PLA2) in blood. The PLAC test is a new way to measure increased risk of Coronary Heart Disease (CHD).

Operating as both a national reference laboratory and a full-service laboratory for the University of Utah Hospital, ARUP strives to continually improve patient care. ARUP believes the addition of the PLAC test will be highly beneficial to many patients at risk for CHD, and expects to begin testing August 1, 2004. "As a reference laboratory focused on bringing clinically relevant new technology to patient care practice, we view this relationship with diaDexus with great excitement and promise," said Ronald L. Weiss, M.D., M.B.A., president and COO of ARUP.

"We are pleased that ARUP is adding the PLAC test to their Cardiac Risk Assessment menu as the science and clinical evidence supporting Lp-PLA2 as a marker of coronary risk continue to gain support and acceptance within the medical community," said Patrick Plewman, CEO of diaDexus.

The test, developed by diaDexus, Inc., is cleared by the U.S. Food and Drug Administration to aid in the prediction of an individual's risk for a CHD event, in conjunction with clinical evaluation and patient risk assessment. Lp-PLA2 has been identified as an independent cardiac risk marker in a number of large patient groups, including the West of Scotland Coronary Prevention cohort (WOSCOPS), published in the New England Journal of Medicine, and the Atherosclerotic Risk in Community cohort (ARIC), published in Circulation in February 2004.

CHD 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. Therefore, novel risk factors, like Lp-PLA2, can help assess CHD risk in patients with low LDL cholesterol.

ARUP joins Mayo Medical Laboratories and Quest Diagnostics Incorporated in offering the PLAC test.

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. More information about the company and the PLACT test may be found at www.diaDexus.com and www.plactest.com.

About ARUP Laboratories
ARUP Laboratories is a national clinical and anatomic pathology reference laboratory owned by the University of Utah. With nearly 1,700 employees, ARUP offers in excess of 2,000 tests and test combinations, ranging from routine cytology screens to highly esoteric molecular and genetic assays. Rather than competing with its clients, ARUP chooses instead to support clients' existing test menus by offering highly complex and unique tests which enhance their abilities to provide local and regional laboratory services. ARUP's clients include more than half of the nation's university teaching hospitals and children's hospitals, as well as multihospital groups, major commercial laboratories, group purchasing organizations, military and government facilities, major clinics, and major pharmaceutical firms. In addition, ARUP is a worldwide leader in innovative laboratory research and development, led by the efforts of the ARUP Institute for Clinical and Experimental Pathology, LLC. Further information on ARUP Laboratories can be obtained on the Internet at www.aruplab.com.