agglutination techniques are used to detect antibodies produced in response to a variety of viruses and bacteria, as well as autoantibodies, which are produced against the self in autoimmune diseasees. for example, assays exist for rubella virus, rotavirus, and rheumatoid factor, and an excellent la test is available for cryptococcus. agglutination techniques are also used in definitive diagnosis of group a streptococcal infection.