What Does Cutoff Mean?
The term cutoff, when used in the context of drug testing, refers to the minimum concentration of a drug or its metabolite that must be present in a test specimen for the result to be considered positive. Cutoff levels vary based on the type of testing used. These cutoff levels, or concentrations, are used for urine drug testing as required by the federal Department of Transportation (DOT). A test specimen that indicates the presence of a targeted drug at a concentration below the cutoff level will be considered a negative result. The cutoff level for each drug and its metabolite, both for initial and confirmatory testing are determined by the DOT. The term cutoff may also be written as cut-off or cut off.
WorkplaceTesting Explains Cutoff
Department of Transportation (DOT) guidelines for urine drug testing do not categorize test results as positive unless the concentration of a targeted drug or its metabolite is equal to or above a minimum cutoff level. This allows for a margin of error in testing and prevents a positive finding in instances where a person has only accidental or environmental exposure to prohibited drugs.
Expressed as nanograms per milliliter (ng/mL), the cutoff level for each drug for which DOT testing is required differs. For example, the cutoff level for an initial or screening drug test for marijuana metabolites is 50 ng/mL. The cutoff level for an initial drug test for cocaine or its metabolites is 150 ng/mL.
If the cutoff level is reached or exceeded in the initial drug test, a confirmatory test is conducted. The cutoff levels for confirmatory testing are different than those of the initial drug test because a different testing methodology is used. The initial screening test will use an immunoassay based test while confirmation testing uses a form of gas chromatography mass spectrometry. In the case of marijuana, a confirmation test is considered positive if the concentration of the analyte THCA in the test specimen equals or exceeds 15 ng/mL.
Under DOT rules, a drug test that indicates the presence of a prohibited drug at less than the cutoff concentration is reported as a negative result. A result may only be reported as positive if the test specimen contains a concentration of the drug or drug metabolite that exceeds the prescribed cutoff amount. These cutoff levels are defined by statute and found at 49 C.F.R. 40.87.