What is direct ELISA? What are its advantages and disadvantages?
The direct ELISA uses the method of directly labeling the antibody itself. Microwell plates are coated with a sample containing the target antigen, and the binding of labeled antibody is quantitated by a colorimetric, chemiluminescent, or fluorescent end-point. Since the secondary antibody step is omitted, the direct ELISA is relatively quick, and avoids potential problems of cross-reactivity of the secondary antibody with components in the antigen sample. However, the direct ELISA requires the labeling of every antibody to be used, which can be a time-consuming and expensive proposition. In addition, certain antibodies may be unsuitable for direct labeling. Direct methods also lack the additional signal amplification that can be achieved with the use of a secondary antibody.
