Drug Testing Information

Drug Metabolism

Most drugs are changed by the body (metabolized) prior to elimination in the urine. In some cases both the parent drug and its metabolite(s) are present, in other cases only the metabolite is present.

Drug Detection and Identification


Screens are performed by Immunoassay . This test is based on the biological interaction of an antibody with a drug and/or its metabolite. This test is sensitive to drug groups as opposed to a specific drug or its metabolite. It is good at detecting drugs when they are present but is subject to interference, which can result in false positives. Screen results must be confirmed in order for KNOX Laboratory to provide court testimony.

Confirmation testing is performed by Gas Chromatography with Mass Spectrum detection (GC/MS). This test is based on the physical and chemical properties of the specific drug or metabolite to be measured. Drug identification is achieved BOTH by chromatographic retention time and by Mass Spectrum, which is the "drug fingerprint." This test is very specific and robust with respect to interference. This confirmation test is legally defensible evidence of drug use.

GC/MS Confirmation Reporting. Results are reported as POSITIVE according to the Substance Abuse and Mental Health Services Administration (SAMHSA) cut-off levels. When detectable quantities of a drug are found below the cutoff level the result is DETECTED. In other words, KNOX Laboratory will only report a POSITIVE result when the levels are above SAMHSA cutoff levels for that substance.

 


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