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The sensitivity of an onsite drug test is heavily dependent on a few different variables; the cut-off level, the drug being tested for, and the type of test.
Sensitivity- Measure of how often a test is able to correctly identify the substance within the sample as a true positive. The more sensitive a test the lower cutoff levels they possess allowing them to detect minute amounts of the tested substance. Low levels of sensitivity will produce more false negative results.
Cut-off Levels – The minimum concentration of a drug or metabolite required to be in a sample to cause a positive result
Please take note of the cut-off levels for urine tests and notice that the sensitivity (the cut-off level) is different depending on the drug being tested for. These are fairly common cut-off levels of tests within the marketplace but customizations of the cut-off levels are possible if necessary. Urine tests are testing for the metabolites that the parent drugs break down into, so the detection window appears later than that of a saliva test.
Please take note below that the saliva tests cut-off levels are lower than that of urine. Saliva tests therefore are more sensitive than urine tests, however this is simply because they need to be in order to detect the smaller amounts of a drug that typically appears in a person’s saliva. Saliva test detect both the parent compound of a drug present and sometimes the metabolites depending on the drug used. Drugs will appear in the saliva by either direct deposition or by passive diffusion through the bodies’ blood stream. For example the parent drug cocaine and its main metabolite benzoylecgonine (BE) and ecgonine methyl ester (EME) can both be present in saliva shortly after cocaine use. Salivary glands within the mouth are continuously secreting fluid and have high blood flow. The cocaine transfers from the blood to the glands resulting in it appearing in the oral fluid.
Please always remember that onsite UA’s provide qualitative results and once you have a presumptive positive you must send the sample to a lab for confirmation. LCMS and GCMS testing has a considerably higher level of sensitivity and can provide quantitative results as well.