Competitive Assay Manufacturing Services

Competitive assays are particularly useful for analytes that are too small to contain multiple antibody binding sites such as traditional pharmaceuticals and illicit drugs-of-abuse. During the competitive assay test process, the sample migrates to the testing area of the membrane by capillary action, mobilizing all antibody conjugates to a region containing immobilized drug antigen. In the absence of the drug or if the drug concentration is below the cutoff limit in the sample, the colored antibody conjugates are captured by the immobilized drug antigen in the test region, giving a burgundy-colored band, or T-line. However, if the target drug is present in the sample at sufficient concentration, it will compete for these limited antibody binding sites, preventing the formation of the burgundy T-line. The control line (C-line) serves as internal quality.