The U.S. Department of Transportation (DOT) issued an interim final rule (IFR) to prevent employees in transportation industries who may naturally produce highly dilute urine specimens from being unfairly found to have violated the department's regulations. The rule expands the definition of dilute tests and changes the amount of a chemical called creatinine in a urine specimen that triggers a finding that the individual has refused to take a drug test. The new rule takes effect immediately. Under current U.S. DOT rules, 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 U.S. DOT rules equivalent to failing a drug test. Medical and scientific experts now believe that some highly dilute specimens should not necessarily trigger a violation of the rules.