Fig. 1. Immunologic tests for antigen detection of infectious agents. AGG, latex or coagglutination; DFA, direct fluorescent antibody test; IFA, indirect fluorescent antibody test, RIA, radioimmunoassay; EIA enzyme immunoassay. F indicates fluorescein or similar luminescent compound. E indicates an enzyme such as horseradish peroxidase, and S indicates a substrate such as hydrogen peroxide.