microtiter plate and the sample to be tested is added after a certain period of incubation to allow formation of an antibody antigen complex a second antibody labeled with a reporter molecule capable of inducing a detectable signal is added and incubation is continued to allow sufficient time for binding with the antigen at a different site resulting with a formation of a complex of antibody antigen labeled antibody the presence of the antigen is determined by observation of a signal which may be quantitated by comparison with control samples containing known amounts of antigen all patents and publications mentioned in this specification are indicative of the levels of those skilled in the art to which the invention pertains all patents and publications are herein incorporated by reference to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference it is to be understood that while a certain form of the invention is illustrated it is not to be limited to the specific form or arrangement herein described and shown it will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown and described in the specification and drawings.