When drugs have been identified during the initial drug screening test, a second test is carried out, known as a confirmatory drug test or confirmation testing. The purpose of this follow-up test is to identify the type and number of drugs or drug metabolites present in the sample. It is conducted using a new sample, or aliquot, taken from the same specimen. Sometimes a directed analysis will also be used to refer to a confirmation test. Often times, a confirmation test is sometimes referred to as a directed analysis.

Drug tests may be administered for employment screening, public safety, or in accordance with a court order. In order to effectively eliminate the possibility of a false positive result, it is usual practice in the industry to conduct a confirmatory test using a different scientific approach than the initial test. As a certified forensic toxicology lab, we are required to verify all positive results before reporting them. (Read more about the lab process & the role of a Medical Review officer)

Depending on the type of specimen being analyzed, the confirmatory test uses either gas chromatography- mass spectrometry (GC-MS) or liquid chromatography- mass spectrometry. The most accurate confirmation technique for evaluating drugs of abuse is GC-MS analysis.

A complex drug mixture can be separated out in this step, and each drug will be sent to the mass spectrometer at a certain point in the run. This time is known as the retention period of a specific drug on the liquid chromatography column. The retention time is a criteria used to determine if a drug is positively identified.

Because the device is looking for specific substances and drug metabolites, confirmation testing takes longer to perform than screening. After the screening results have been evaluated, confirmation of positive results can take another 24-48 hours.

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Lia Robinson

I am a person who views life positively in all aspects. I enjoy a wide variety of activities, sights, and experiences.

Born & raised in Harlem, New York. A few of my interests include blogging, spending time with close friends, reading educational books, and traveling around the world. To find out more about me, get in touch.

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