When a Urine Drug Screen is being performed a chemical reaction occurs within each test strip depending on what substance (Drug) one is testing for. The reaction is called Immunoassay. Typically the active and control bands on the test strip will change from colorless to violet when the test strip is exposed to urine that contains no reacting substance (Drug). The active band will remain colorless and control band on the test strip will change from colorless to violet when the test strip is exposed to urine that contains a reacting substance (Drug) that we are testing for. Unfortunately there are many over-the-counter and prescription medications that contain chemical groups similar to the substances (Drugs) that we are testing for. These similar chemical groups can cross react and trigger a test strip band to remain colorless on an immunoassay. This is what we call a NON-NEGATIVE drug screen. It serves only as an indication that a substance similar to a drug we are testing for is dissolved within the urine.
In the event a urine drug screen is found to be non-negative you MUST proceed with the confirmation process.
UDS Confirmation process: