Quest Diagnostics Incorporated , the nation's leading provider of gene-based medical testing, announced that it has begun to offer a test to enable physicians to detect a new risk factor for cardiovascular disease by measuring levels of the enzyme Lp-PLA2 (lipoprotein-associated phospholipase A2). Elevated levels of Lp-PLA2 indicate that a patient is at an increased risk of suffering a cardiovascular event, such as a heart attack. Importantly, in some cases, this test identifies patients who do not have other apparent risk factors. The Lp-PLA2 test is designed to be used in conjunction with clinical data and other diagnostic markers, such as LDL. Quest Diagnostics performs the test under an agreement with diaDexus, Inc., based in South San Francisco, California.

"This exciting new marker for cardiovascular risk assessment has the potential to become an integral part of our cardiovascular test offering, providing additive risk assessment information when used in conjunction with existing risk markers, including low- and high-density lipoprotein cholesterol (LDL and HDL), triglycerides, homocysteine and high-sensitivity C-reactive protein," said Richard E. Reitz, M.D., Medical Director at Quest Diagnostics Nichols Institute, the company's esoteric testing laboratory and research and development center.

The potential clinical value for Lp-PLA2 was first suggested in a key study of individuals in Scotland who had a high risk for heart attack, which was published in The New England Journal of Medicine in October 2000(1). The study described Lp-PLA2 as a novel independent risk factor that may be used to identify and manage patients at risk of a cardiac event. More recently, the results from the NIH-sponsored ARIC study were presented at the American College of Cardiology, Chicago in April, 2003 at the Late Breaking Clinical Trials event by Dr. Christie Ballantyne, Director, Center for Cardiovascular Disease Prevention at Baylor College of Medicine and DeBakey Heart Center in Houston. Dr. Ballantyne found that individuals with normal levels of LDL-cholesterol had more than twice the risk of having a heart attack if their Lp-PLA2 levels were elevated.

"One-third to one-half of individuals with coronary heart disease have normal LDL levels, clearly indicating the need for novel risk factors," said Dr. Ballantyne. "By adding Lp-PLA2 to its cardiac risk assessment menu, Quest Diagnostics is making this valuable new test widely available to physicians and their patients throughout the country." Cardiovascular disease is the leading cause of death in the U.S. According to the American Heart Association, more than 500,000 people die each year from heart attacks in the U.S., and approximately 60 million Americans have some form of cardiovascular disease, making early detection of risk factors crucial.

Quest Diagnostics Incorporated is the nation's leading provider of diagnostic testing, information and services, providing insights that enable physicians, hospitals, managed care organizations and other healthcare professionals to make decisions to improve health. The company offers the broadest access to diagnostic laboratory services through its national network of laboratories and patient service centers. Quest Diagnostics is the leading provider of esoteric testing, including gene-based medical testing, and empowers healthcare organizations and clinicians with state-of-the-art connectivity solutions that improve practice management. Additional company information can be found on the Internet at: www.questdiagnostics.com.

The statements in this press release which are not historical facts or information may be forward-looking statements. These forward-looking statements involve risks and uncertainties that could cause actual results and outcomes to be materially different. Certain of these risks and uncertainties may include, but are not limited to, unanticipated expenditures, changing relationships with customers, payers, suppliers and strategic partners, competitive environment, changes in government regulations, conditions of the economy and other factors described in the Quest Diagnostics Incorporated 2002 Form 10-K and subsequent filings.

  (1) Packard CJ, O'Reilly DSJ, Caslake MJ, et al. Lipoprotein-associated
      phospholipaseA2 as an independent predictor of coronary heart disease.
      N Eng Med 2000; 343:1148-55.

SOURCE: Quest Diagnostics Incorporated

CONTACT: Jennifer Somers, +1-201-393-5700, or Investors - Laure Park,
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Web site: http://www.questdiagnostics.com/