Quest Diagnostics Incorporated , the nation's leading provider of diagnostic testing, information and services, announced that it has developed and is now offering a gene-based blood test to detect genetic mutations associated with congenital adrenal hyperplasia, a condition that causes females to accumulate male sex hormones. Congenital adrenal hyperplasia (CAH) is a relatively common disease that can affect normal growth and development and may influence how the body deals with the stress of illness or injury. It is most often caused by deficiency of a specific enzyme, 21-hydroxylase. Some forms of the disorder that occur infrequently may cause life-threatening illness. A mild form of the disease that occurs more frequently is a possible cause of infertility in women.

The new test, which is available to physicians nationwide, detects 90-95 % of genetic mutations associated with congenital adrenal hyperplasia. This test can be of value to individuals with the disease as well as families with a history of CAH. In addition, obstetricians can use the gene-based test during a patient's pregnancy to guide the use of therapy to prevent malformations in affected female fetuses. Currently, CAH testing is a part of a neo-natal blood screen in the majority of states to identify infants with the severe form of the disease.

CAH may be inherited by both males and females. The non-classical mild form of the disease is relatively common, occurring in 1 of every 1,000 births, but is considerably more frequent in certain ethnic groups. The classical severe form is rare and occurs in only 1 in every 15,000 newborns.

Quest Diagnostics developed the new CAH test at its Nichols Institute esoteric testing laboratory in San Juan Capistrano, California. The new test, on which a Quest Diagnostics patent is pending, uses a proprietary gene-amplification procedure through which the 21-hydroxylase gene, a defective form of the gene on the same chromosome and products of recombination between those two genes are prepared for analysis by DNA mini-sequencing.

"This new gene-based test will be available immediately to doctors and their patients across the country," said Delbert A. Fisher, M.D., Vice President, Science and Innovation. "The Nichols Institute has a 30-year history of providing state-of-the-art testing and consultative services for endocrine disorders. Release of the new CAH test continues on that tradition and marks a new focus on molecular endocrinology."

Quest Diagnostics Incorporated is the nation's leading provider of diagnostic testing, information and services, providing insights that enable healthcare professionals to make decisions that improve health. The company offers the broadest access to diagnostic testing services through its national network of laboratories and patient service centers, and provides interpretive consultation through its extensive medical and scientific staff. Quest Diagnostics is the leading provider of esoteric testing, including gene-based medical testing, and provides advanced information technology solutions to improve patient care. Additional company information is available 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, competitive environment, changes in government regulations, changing relationships with customers, payers, suppliers and strategic partners and other factors described in the Quest Diagnostics Incorporated 2003 Form 10-K and subsequent filings.

SOURCE: Quest Diagnostics Incorporated

CONTACT: Laure Park, Investors, +1-201-393-5030, and Gary Samuels,
Media, +1-201-393-5700, both of Quest Diagnostics Incorporated

Web site: http://www.questdiagnostics.com/