How Drug Test Kits Work
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The Home Drug Test Kit is a lateral flow, one-step panel immunoassay for the qualitative detection of drugs and drug metabolites in human urine. The Home Drug Test Kit is based on the principle of the highly specific immunochemical reactions of antigens and antibodies, which are used for the analysis of specific compounds in biological fluids. It is a rapid, visual, competitive panel immunoassay. The speed and sensitivity of immunoassays have made them the most widely accepted method for screening urine for drugs of abuse.
The Home Drug Test Kit is a one-step immunoassay in which a chemically labeled drug (drug conjugate) competes with the drug, which may be present in urine for limited antibody binding sites. The test device contains a membrane strip, which is pre-coated with drug conjugate on the test band. A colored anti-drug monoclonal antibody-colloidal gold conjugate pad is placed at the right end of the membrane. When drug is absent in the urine, the solution of colored antibody-colloidal gold conjugate and urine moves upward, chromatographically by capillary action, across the membrane. This solution then migrates to the immobilized drug conjugate zone on the test band region. The colored antibody-colloidal gold conjugate attaches to the drug conjugate to form a visible line as the antibody complexes with the drug conjugate. Therefore, the presence of a visible colored band in the Test Region (T) indicates a negative result. When drug is present in the urine, the drug/metabolite antigen competes with the drug conjugate on the test band region for the limited antibody binding sites on the anti-drug monoclonal antibody-colloidal gold conjugate. When a sufficient concentration of drug is present, it will fill the limited antibody binding sites. This will prevent attachment of the colored antibody-colloidal gold conjugate to the drug conjugate zone on the test band region. Therefore, the absence of a visible colored band in the Test Region (T) indicates a positive result.
A control band with a different antigen/antibody reaction is also added to the membrane strip at the Control Region (C). This control line indicates that the device is working properly and that sufficient volume of sample has been added. It should always appear, regardless of the presence of drug or metabolite. Therefore, negative urine will produce two colored bands and positive urine will produce only one band.Learn more about... Keys' Drug Testing Items