MarijuanaScan tests are based on the principle of specific immunochemical reaction between antibodies and antigens to analyse particular compounds in human urine specimen. The assay relies on the competition for binding antibody between drug conjugate and free drug which may be present in the urine specimen being tested. When a drug is present in the urine specimen, it competes with drug conjugate for the limited amount of antibody-dye conjugate. When the amount of drug is equal or more than the cut-off level of 50 ng/mL, it will prevent the binding of drug conjugate to the antibody. Therefore, a positive urine specimen will not show a coloured band on the test line zone, indicating a positive result, while the presence of a coloured band indicates a negative result. A control line is present in the test window to work as procedural control. This coloured band should always appear on the control line zone if the test device is stored in good condition and the test is performed appropriately. The control line serves to validate the test results.