Cutoff concentration

A cutoff concentration is the threshold, set by a testing program, at or above which a drug test reports a result as non-negative or positive.

Screening and confirmatory tests each have their own cutoff, usually expressed in nanograms per milliliter, and the confirmatory value is typically lower. Below the cutoff the result reads negative even if a small amount of the compound is present. Cutoffs are chosen to balance sensitivity against the risk of results from incidental exposure, and federal programs publish theirs.

For cannabinoid products the cutoffs that matter are those for THC-COOH, the metabolite of delta-9 THC. A product containing trace THC may or may not produce a result below the cutoff, depending on amount used, frequency, body composition and metabolism, and no product can guarantee that outcome. Employer programs outside federal rules may set their own thresholds, so the figure that applies to any specific test is the program's, not a general one.