Immunoassay: a test used to detect the presence or quantity of a substance (as a protein) based on its capacity to act as an antigen or antibody.

Antibody: An antibody is a protein produced by immune cells in response to stimulation by an antigen.

Antigen: A molecule capable of inducing an immune response.

Rapid TOX Cup® II uses one-step lateral flow immunoassays that utilize highly specific reactions between antibodies and antigens. The test strip consists of a membrane strip with an immobilized drug conjugate. A colloidal gold-labeled antibody complex is dried at one end of the test strip. In the absence of a drug in the urine specimen, the capillary movement of the urine allows contact between an antibody and the immobilized drug conjugate to produce an antibody-antigen reaction to form a visible line in the ‘test’ area. A control line, comprised of a different antibody-antigen reaction is also present on the membrane strip. The control line is not influenced by the presence or absence of a drug analyte in the urine specimen and therefore should be present in all reactions.

The formation of two or more visible lines (control and test lines) occurs when the test is negative or below the cut-off for the drug. The formation of a control line, and the absence of a test line are indicative of a preliminary positive result.