The First SignTM Drug of Abuse Test Test is a one-step membrane immuno-chromatographic test (6) based on antigen/antibody complexation and is used for the analysis of Drug of Abuse Test and its metabolite present in the test sample. The assay is based on the competition between the drug or drug metabolite in the sample and a drug conjugate immobilized on a porous membrane support for limited antibody sites on the colored microspheres. Test urine is delivered into a sample site located at one end of the porous membrane. When the drug is present in the urine test sample, the drug or drug metabolite competes for the limited antibody sites on the microspheres. When an adequate amount of drug is present attachment of the colored microspheres to the probe site on the membrane. Therefore, a positive urine sample will inhibit the formation of a precipitin line at the probe area. A reference or control line with a secondary antibody reaction is added to the membrane test to indicate that the test is viable. This control line should always be present before making any test interpretation. Normally, a negative urine sample will produce two colored lines (the formation of a visible precipitin at the test zone in addition to the control line), and a positive urine sample will show only one line (the control line)