Cocaine, marijuana and methamphetamine use continues to climb among workers in the United States, though opioid use is down, according to a study released Tuesday by Madison, New Jersey-based Quest Diagnostics Inc. Overall, positive urine drug testing among the combined U.S. workforce in 2016 was 4.2% — an increase over the 2014 rate of 4%, according to the latest Quest Diagnostics Drug Testing Index. This represents the highest annual positivity rate since 2004, when positive tests were at 4.5%, the study shows. The results were also broken down by drug type.