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.
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