Immunoassay Screening

Definition - What does Immunoassay Screening mean?

Immunoassay screening is a chemical test designed to determine the presence of a specific substance (an antigen) within a testing medium. It is the most common type of drug test performed. With respect to drug and alcohol testing, the antigen is the parent drug or metabolite within the testing medium. This chemical test involves a reaction between the antigen and a natural or synthetically derived antibody. The antigen will bind to the antibody based on a common binding site to determine the presence of the antigen within the testing medium.

WorkplaceTesting explains Immunoassay Screening

The testing mediums commonly seen with this type of testing are urine, blood and oral fluid. The drug or drug metabolite has a common binding site with its antibody within the testing device, much like a lock and key. A testing device could be either a laboratory immunoassay machine or in the field with a point-of-collection test (similar to a simple pregnancy test). Although rare, there are instances when immunoassay screening may cause a false positive or false negative when a substance with a similar binding site binds with the antibody. As a result, it is always recommended that a positive immunoassay screening result is verified using a different process, such gas chromatography mas spectography.

This definition was written in the context of Drug Testing
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