How drug tests work: the technology

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Drug testing seems simple – you just run the test and read the result. However, behind this simplicity hides a lot of complexity.

Drug tests use competitive lateral flow immunoassay technology. Here’s what the italicised words mean, broken down:

Competitive format: this means that two lines = negative, one line = not-negative. This is the opposite of a sandwich format test, where two lines is positive (the most common example of this is a pregnancy test).

Lateral flow: the urine or saliva starts at one end of the strip, and flows laterally (along) the strip.

Immunoassay: a test for the presence of a molecule, using antibody/antigen reactions.

This is a complicated and interesting technology, which enables quick point-of-care testing.