In drug testing, this is the minimum amount of a drug metabolite that must be present in a sample to determine if it is a negative or positive test. Cutoff levels are established to avoid false positive test results due to incidental exposure to a substance. For example, a person who has breathed in second-hand marijuana smoke may have traces of marijuana show up in their urine or saliva sample but this will be below the minimum amount needed for a positive test, meaning the test will be negative.