Solid phase multi-analyte assay

A method for determining the amount of an analyte of interest in a sample, the method comprising contacting a solid phase composition with i) an antibody specific for the analyte of interest and ii) the sample under competitive binding conditions, and determining the amount of the analyte of interest in the sample;

• wherein:
• the solid phase composition comprises a polystyrene solid phase support and at least two different conjugates, wherein each conjugate comprises an albumin covalently conjugated to a drug of abuse or metabolite thereof selected from the group consisting of benzoylecgonine, an amphetamine, tramadol, PCP, morphine, oxycodone, methadone, cotinine, a benzodiazepine, buprenorphine, fentanyl, and a cannabinoid;
• wherein the antibody specific for the analyte of interest binds to one of the at least two different conjugates;
• the analyte is a drug of abuse or a metabolite thereof;
• the at least two different conjugates are bound noncovalently or via adsorption to the polystyrene solid phase support;
• the at least two different conjugates are randomly affixed as a mixture to a single solid phase component of the polystyrene solid phase support, wherein the polystyrene solid phase support comprises a plurality of single solid phase components, and each single solid phase component of the polystyrene solid phase support comprises the at least two different conjugates;
• and
• the antibody specific for the analyte of interest is labeled or a labeled secondary antibody is introduced which is specific for the antibody specific for the analyte of interest.