The rule expands the definition of “dilute tests” and changes the amount creatinine in a urine specimen that triggers a finding that the individual has refused to take a drug test.

“Based on the our drug testing experience and recent scientific and medical information, we have concluded that we should change the way we treat highly dilute specimens,” said Ken Edgell, acting director of the department’s Office of Drug and Alcohol Policy Compliance. “We want to take every precaution to ensure that a transportation employee cannot be charged unfairly with having substituted some other substance for his or her urine specimen.”

Under current USDOT rules, which are directly taken from the Department of Health and Human Services (HHS) program documents, a urine specimen with five milligrams of creatinine per deciliter of urine or less is regarded as “substituted.” A “substituted” test is considered a refusal to take a drug test, a violation of USDOT rules equivalent to failing a drug test.

The new rule takes effect immediately.