• Cutoff Level (Cutoff Concentration):
    The concentration of a compound, in fluid, required to yield a positive test reading, typically reported in nanograms (1 billionth of 1 gram) of the compound per milliliter of fluid (ng/mL). Samples with a concentration of compound equal to or greater than the cutoff level are reported positive. Samples with a concentration of compound below the cutoff level are reported negative. A lower cutoff level indicates greater ability to detect the compound.