Adulterated specimen: A specimen that contains a substance that is not expected to be present in human urine, or contains a substance expected to be present but is at a concentration so high that it is not consistent with human urine.

Antigen: A substance that when introduced into the body stimulates the production of an antibody. Antigens include toxins, bacteria, foreign blood cells, and the cells of transplanted organs.

Creatine: A white crystalline nitrogenous substance C4H9N3O2 found especially in the muscles of vertebrates either free or as phosphocreatine

Cutoff Level (Threshold): The defined concentration of a substance in a specimen at or above which the test is called positive and below which it is called negative. This concentration is usually significantly greater than the sensitivity of the assay.

Dilute specimen. A specimen with creatine and specific gravity values that are lower than expected for human urine.

Gas Chromatography: A process in which the specimen is vaporized and injected into a stream of carrier gas (as nitrogen or helium) moving through a column containing a stationary phase composed of a liquid or particulate solid and is separated into its component compounds.

Immunoassay: A laboratory technique that makes use of the binding between an antigen and its antibody in order to identify and quantify the specific antigen or antibody in a sample.
Initial Test

Invalid drug test: The result of a drug test for a urine specimen that contains an unidentified adulterant or an unidentified interfering substance, has abnormal physical characteristics, or has an endogenous substance at an abnormal concentration that prevents the laboratory from completing or obtaining a valid drug test result. There can be several reasons for an invalid or unsuitable result.

Examples include:

• Not suitable for testing
• pH is out of range
• Temperature of the specimen is out of range
• GC/MS interference
• Immunoassay interference
• Interfering substance
• Creatinine < or = 5 but the specific gravity is within normal limits
  

Mass Spectrometry: An instrumental method used in conjunction with Gas Chromatography that provides accurate information about the molecular mass and structure of complex molecules. This technique can identify and quantify extremely small amounts of drugs or metabolites by their mass-fragment spectrum.

Medical Review Officer: A medical professional, most often a licensed physician, who is responsible for receiving and reviewing all confirmed “positive ” drug-test results from the laboratory. The MRO is generally responsible for contacting all individuals testing “positive ” to inquire about possible prescription or over-the-counter medications which may have caused a “positive ” test result. The MRO must have knowledge of substance-abuse disorders and the appropriate medical training in order to interpret and evaluate “positive ” test results, together with an individual’s history and any other relevant medical information.

Metabolite: A compound produced from the chemical changes of a drug in the body.