LYNDHURST, N.J., May 16, 2005 - The use of amphetamines among general workforce employees continued to grow in 2004, according to the semi-annual Drug Testing Index® released today by Quest Diagnostics Incorporated (NYSE: DGX), the leading provider of employer drug testing services in the United States.

Amphetamines use, which grew rapidly between 2000 and 2003, continued to grow in 2004, although at a slower rate. Among general U.S. workforce employees, the incidence of positive drug tests attributed to amphetamines rose by approximately 6% in 2004 from 2003, reaching 0.52% of all drug tests that look for amphetamines among this group of workers. During 2003 amphetamines positivity was 0.49%. Between 2000 and 2003, year-over-year growth rates for amphetamines positivity had been 16%, 17% and 44%, respectively.

Among Federally-mandated, safety-sensitive workers, the incidence of positive drug tests attributed to amphetamines also grew by 6%, reaching 0.31% of all drug tests that look for the use of amphetamines among these workers. During 2003, amphetamines positivity was 0.29%.

"The use of amphetamines among workers continued to grow in 2004," said Barry Sample, Ph.D., Director of Science and Technology for the Employer Solutions division of Quest Diagnostics. "However amphetamines use among workers grew at a slower pace, when compared to previous years."

Overall, the drug positivity rate for U.S. workers remained unchanged at 4.5% from 2003. The positivity rate is the number of positive test results compared to the total number of drug tests performed by Quest Diagnostics. Quest Diagnostics performed more than 7.2 million workplace drug tests from January to December 2004.

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